My friend Ed woke up this morning to find his website defaced. Upon the now altered web page, he found this number sequence:

$237,\ 3566,\ 57069,\ \color{green}{???},\ 14600926,\ 233811181$

One of the numbers is missing, can you figure out what it could be?

Note: the story is fictional and can be used as a hint. Additional hints may be added if the puzzle remains unsolved.

  • 1
    $\begingroup$ 404 ? Not found... $\endgroup$ Aug 13, 2020 at 15:01

1 Answer 1


The missing number is:


Convert each number to it's hexadecimal equivalent to get a word. 237 in Hex is ED, 3566 is DEE, 57069 is DEED, 14600926 is DECADE, and 233811181 is DEFACED.
Each number keeps the previous letters but adds one more, while still making a word. That means the missing number has to either add A or C to DEED (because DECADE is DEED with an A and a C added.
The only 5 letter word I could create from DEED + A or C was CEDED, which converted from hex to decimal came out to 847341.
(My first answer was ADDED, before I realized I added a D and removed an E...)

  • $\begingroup$ That is correct! Very impressive, I expected it would take much longer. $\endgroup$ Aug 13, 2020 at 15:07
  • $\begingroup$ I was lucky, I had a professor use 233811181 in a lesson about conversions because of it's prime number status; probably wouldn't have remembered it if not for the comment about the story having a hint. $\endgroup$ Aug 13, 2020 at 15:10
  • $\begingroup$ That's very interesting. I didn't realize it was prime, but of course that does come up when you Google the number. The other rot13(frira yrggre bcgvbaf jrer npprqrq naq rssnprq). $\endgroup$ Aug 13, 2020 at 15:20

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