Questions tagged [number-sequence]

A puzzle in which the hidden pattern behind a given sequence of numbers (and, often, the next term) is to be found. Use with [sequence]

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Mysterious message from the NoSlaves™ Calculator Co

So my son is starting to show an interest in mathematics, and being the awesome dad that I am, I decided to buy him a basic calculator. Being the cheapskate that I am, I ordered the cheapest one I ...
Alconja's user avatar
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60 votes
6 answers
5k views

What makes an Interesting Puzzle™?

This puzzle is based off the What is a Word™ and What is a Phrase™ series started by JLee and their spin-off What is a Number™ series. I like What is an Adjective Noun™ puzzles. Here are a few I ...
boboquack's user avatar
  • 22k
59 votes
4 answers
10k views

Interview Question or Pathbreaking puzzle

I thought this changes the way series of numbers are looked at 1 1 1 2 1 1 2 1 1 Write down the next three lines
skv's user avatar
  • 5,002
59 votes
1 answer
56k views

My dead mom left behind some number code

Background: I actually do not know the answer to this puzzle, but can answer any questions you may have. My mom who is now deceased had this series of numbers written in her notebook, that don't seem ...
Cain Smith's user avatar
40 votes
3 answers
2k views

What comes next in the sequence? (Counting sheep)

My roommate has insomnia so he was counting sheep to help him sleep. He started with 2986, then continued with 47786, 764586, and 12233386. What sequence is he following, and what was the next number?
DenverCoder1's user avatar
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38 votes
2 answers
3k views

It's my birthday

Just like last year, my age is a number you can score with one dart. The year before that, it wasn't, and it won't be next year. How old am I?
Rupert Morrish's user avatar
37 votes
5 answers
11k views

A very simple puzzle: 1,1,2,1,2,2,3

Here's a simple puzzle, I know that you will find. As long as you can count, It shouldn't take much time. 1 1 2 1 2 2 3 1 2 2 3 Find the next 4 numbers in this sequence.
Kingrames's user avatar
  • 2,697
37 votes
3 answers
9k views

What is the next number in the series: 21, 21, 23, 20, 5, 25, 31, 24,?

I came across a puzzle from a workbook for primary school students who wish to sit in exams for enrolling to selective high schools, which asks about what is the next number in the series. What is ...
Michael May's user avatar
37 votes
2 answers
2k views

A powerful drink

I'm addicted to this stuff. I had my first double when I was 16. There were five of us that night on the town. I didn't think much of it then, but two years later I had another double, and then ...
Darrel Hoffman's user avatar
34 votes
6 answers
9k views

An unusual and very hard number sequence problem

I heard this number sequence problem about 25 years ago from a maths lecturer. What number should go in the place of the question mark in this mathematical sequence: ..., 30, ?, 60, 90, 140, 225, 372, ...
Jaap Scherphuis's user avatar
34 votes
1 answer
1k views

A number sequence in disguise

What number should replace the question mark? Explain why. ...
Prim3numbah's user avatar
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33 votes
1 answer
2k views

Professor Halfbrain and the sum of the digits of all divisors

Yesterday I met professor Halfbrain in the city. The professor looked tired and somewhat exhausted. He told me that he had spent his nights and days with adding up digits of divisors of positive ...
Gamow's user avatar
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33 votes
2 answers
3k views

Ancient machine in the desert... how does it generate its output?

I was walking through the desert and came across an ancient contraption of cogs and gears. It had a series of dials on one side that appeared to allow the input and output of numbers. On the other ...
Alconja's user avatar
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29 votes
1 answer
3k views

That gap is a bit jarring

... but there doesn't seem to be anything missing. $0,1,2,3,4,5,6,7,1527465$ What then could cause that rather large gap?
zennehoy's user avatar
  • 635
28 votes
2 answers
33k views

What is this magic trick with 6 cards featuring numbers between 1 and 60?

I hope this is on topic. I have a set of kids' magic tricks but I have lost the instructions! I was hoping this might be a good place to get some help. Here is the first one. What is the trick and ...
Simd's user avatar
  • 7,845
26 votes
3 answers
1k views

Why aren't the numbers playing nicely anymore?

The natural numbers have gotten in a big fight and split up into groups. If we can't get them back together again, the universe may never be the same! What kind of sense does it make to have three ...
Engineer Toast's user avatar
25 votes
1 answer
3k views

Four is Cosmic!

This is a little puzzle I heard a while back from one of my mathematically inclined friends- I get the sense that it's bounced around a little, so forgive me if you've heard it. There is a sort of ...
Patrick N's user avatar
  • 1,790
25 votes
1 answer
867 views

Oh dear, oh my, how blatant

Looking at the Puzzling Stack Exchange recently, I found a surfeit of number sequence riddles that all look the same! I mean, there's no difference between any of them. I'm sick and tired of all these ...
Austin Weaver's user avatar
24 votes
1 answer
1k views

A predictable sequence

"Four, four, four, ..." droned the random number generating monster. "Are you sure that's random?" I asked. "That's the problem with randomness, you can never be sure!" ...
Matt's user avatar
  • 1,711
23 votes
1 answer
2k views

A brief int counter

The following infinite sequence is used by those taking first steps in maths. 3, 3, 4, 4, 4, 3, 4, 5, 3, 3, 4, 5, 6, 7, ? Find the next number.
Tom's user avatar
  • 70.5k
23 votes
1 answer
4k views

Very simple, yet unsolved, sequence of numbers

A simple sequence of numbers, which I encountered during intermediate school, in my math book. Any person that finished intermediate school possesses the necessary toolbox required to solve this ...
RickardNi's user avatar
  • 365
23 votes
1 answer
1k views

A Sequence That Keeps Changing?

So I get this special sequence of "items" as the following: 2 1 3 4 7 8 2 5 2 3 9 But look! If I put some numbers (randomly) in front of the sequence: 3 4 2 1 3 4 7 8 2 5 2 3 8 And yeah! ...
athin's user avatar
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22 votes
1 answer
1k views

Revenge on OEIS*

First, a story about how I messed up a puzzle: It’s hard to make a simple yet creative number puzzle. After fiddling one late, dark winter evening with different patterns, at last I made a sequence ...
Reinis Mazeiks's user avatar
22 votes
0 answers
2k views

REALLY important days in history

@Z. Dailey asks a mathematical puzzle Important days in history... and to come! with a series of dates in years 1973, 1978, 1983, 1992, 2005. My puzzle asks the question: What is the previous date in ...
Haobin's user avatar
  • 11.7k
20 votes
2 answers
1k views

A symmetrical number sequence

What 5-letter word does this sequence represent? ...
Prim3numbah's user avatar
  • 34.3k
20 votes
1 answer
767 views

What is the last integer in this sequence?

Here are the first several entries in a finite sequence of integers. $$ 31, 45, 71, 89, 91, 94, 111, 112, 118, 121, 126, 131, $$ $$ 134, 135, 139, 143, 144, 145, 148, 158, 161, 189, 193, 194, \dots $$ ...
Rubio's user avatar
  • 41.7k
20 votes
2 answers
2k views

Ernie and the Alien Invasion

Yesterday I dropped in on Ernie to show off my new j-watch. Ernie wouldn't be impressed by instant wrist-mounted access to social media sites like me-tube, tweeter and farce-book so I thought I would ...
Penguino's user avatar
  • 13.9k
20 votes
2 answers
589 views

A real time-waster: the clock of confusion and color

John was doing his math problems like a good child one day until he looked at the clock to see if it was time to sleep. To his dismay, the blasted thing had become another math problem! But this one ...
Mule Donkey's user avatar
19 votes
1 answer
1k views

What kind of puzzle is solved by these sequences of numbers?

Samantha had been fiddling with something at her desk for ages, and constantly scribbling notes on a piece of paper. When my curiosity eventually got the better of me, I wandered over to ask what she ...
Rand al'Thor's user avatar
19 votes
5 answers
806 views

A riddle that has been killing me the whole day

So I'm walking around in London and found the following number riddle. The rules say, that what ever pattern you find, must be true for the rows as well as the columns. The answer in level 1 is for ...
Viktor Jeppesen's user avatar
18 votes
6 answers
2k views

Important days in history... and to come!

The other day I decided I wanted to come up with another simple puzzle before releasing another toughy on puzzling.SE. I came across an interesting series of dates that I wanted to share and see if ...
Z. Dailey's user avatar
  • 3,580
18 votes
1 answer
1k views

How does this addition work (13+7=1130)?

I found this problem on 9gag and I have no idea how to solve it. Here is the question: $13+7=1130$ $88+9=47$ $32+28=2530$ $10+999=1149$ $444+77=61$ $55+111=56$ $21+0=1221$ $7+22=39$ $33+5=38$...
user avatar
18 votes
1 answer
1k views

Describe your ability to solve this number sequence!

Here is a sequence of numbers: 0, 2, 4, 6, 8, -, -, -, 10, 12 Can you fill in the three blanks and thus reveal your excellent puzzle-solving ability?
chasly - supports Monica's user avatar
17 votes
2 answers
1k views

What does this group of numbers represent?

How is this set of 8 numbers - $6, 8, 15, 20, 36, 48, 90$, and $120$ - derived? I could provide hints but it would make it too easy.
Moti's user avatar
  • 2,239
17 votes
3 answers
1k views

How is this number sequence built up and how does it continue?

Can you work out how this number sequence is built up? Can you work out how it continues? 1, 1, 2, 4, 8, 20, 60, 240, 1500, ....... Hint 1 Hint 2 From time to time hints will be updated. Note: ...
tom's user avatar
  • 4,261
17 votes
2 answers
1k views

A geometric sequence using one digit

Give the first few terms of a geometric[1] sequence such that: the sequence is increasing and infinite only one digit is used throughout the sequence the terms are written as base ten ...
Tom's user avatar
  • 70.5k
17 votes
2 answers
931 views

16 number puzzles on a blackboard

I have left you some number puzzles on the blackboard. Solve them and let me know what they spell. Hint:
DenverCoder1's user avatar
  • 10.5k
17 votes
1 answer
759 views

Quality Over Quantities

Your final answer will be a number (or maybe not?) 6.1482925535194332784626433, 15, 70, 5388440228181184467208035634811703511875, 45, 1207432478148385373947988/38313917, 15, 70, ?
stacksfiller's user avatar
  • 10.5k
17 votes
2 answers
1k views

Logically linked numbers

The left and right numbers are linked. What should the last number on the right be, and why? \begin{align} 135759&: 1 \\ 151364&: 4 \\ 255075&: 9 \\ 279422&: 36 \\ 292620&: 91 \\ ...
Jonathan Allan's user avatar
17 votes
1 answer
556 views

Some enigmatic number sequences

Here are some numbers: 959, 233, 14, 36, 105, 45, 784, 120, 1579, 1001, 1111, 90, 841, 1607, 590, 625, 609, 144, 606 And here are the rest of the numbers: 1, 2, 5, 20, 30, 34, 42, 55, 56, 66, 72, 78, ...
phenomist's user avatar
  • 13.6k
17 votes
1 answer
673 views

Rethinking this series on the syllabus

I assigned each person in my class the task of creating a number-sequence, however, 4 of the guys I usually consider to be leaders came back with baffling results. Can you make sense of their work and ...
arbitrahj's user avatar
  • 2,037
17 votes
1 answer
1k views

Creepy video on Youtube, with secret cipher built in

This showed up in r/deepintoyoutube: https://www.youtube.com/watch?v=j1ExfbH4Jew I've posted it around, and no one has solved it. I believe it is a cipher for a couple of reasons, at the end 26 ...
Bill Thorson's user avatar
16 votes
5 answers
2k views

Should the angels play their game?

Two angels in heaven want to play a game. One of them comes up with an arbitrary, computable function from the integers to the integers. The other angel has to guess what it is. The second angel can ...
Kevin's user avatar
  • 1,283
16 votes
1 answer
1k views

Find d this ones stumped me help?

This one is annoying me so much. Got this from a maths teacher.
Jack Coughlan's user avatar
16 votes
1 answer
4k views

Radical IQ challenge

This puzzle is part of the Monthly Topic Challenge #2: IQ Puzzle Parody Can you find out the next one in the sequence, how it's different to the ones before it, and explain the pattern? 1 10 11 20 31 ...
PuzzlingFerret's user avatar
16 votes
2 answers
2k views

What is the next number in the series?

What is the next number of this series? 1 , 4 , 5 , 6 , 7 , 9 , 11 ?
Ram Visagan's user avatar
16 votes
3 answers
837 views

Mathematical cryptic clues

Programming language, after removing loss for you, reverses time (6) Complex arithmetic begins, Turing tests start beforehand (7) Quadruply male doctor Einstein, familiarly (11) Lie on a ...
HTM's user avatar
  • 16.3k
16 votes
1 answer
2k views

Can you find O in this math riddle?

If: R = 1,111 T = 2,222 E = 3,333 N = 4,444 What is O equal to?
diggity's user avatar
  • 620
16 votes
1 answer
1k views

Given these numbers, find the secret word

My son is 12 years old and his task was to find an English word from these numbers: 13; -8; 2; 2; -6; 12; 2; 6; -1; -12 where ...
tenepolis's user avatar
  • 263
15 votes
9 answers
5k views

Is this sequence that hard?

I published a sequence that seems difficult to the general public, so I've thought of posting it here. It has a very simple logic (language independent). Can you figure out the next number?
Edgar G.'s user avatar
  • 1,003

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