# You have (3^2 + 2^3 + 2^2) Guesses Left. Figure out the Last one

Getting bored of all the sequences (including mine)?

Here is a little different one for you.

What is the last one in the following:

C, H, O, P, S, ?

Tell me why?

• Is the no-computers tag necessary? – Brandon_J Jun 6 '19 at 1:23
• People can search for patterns just they do in oeis..that’s why I put it in..anyway most of my sequences wont be found in oeis. – Uvc Jun 6 '19 at 1:31
• But OEIS is the online encyclopedia of integer sequences, and this is not an integer sequence. – Brandon_J Jun 6 '19 at 1:32
• That would be a computer search..anyway I err on the side of caution . – Uvc Jun 6 '19 at 1:34

N

Reasoning

These are chemical symbols representing the six most important chemical elements whose covalent combinations make up most biological molecules on Earth ("six elements of life"): carbon, hydrogen, oxygen, phosphorus, sulphur, nitrogen

• Any explanation for the order? (i.e. why wasn't it H, C, ?, O, P, S in the puzzle?) – Rand al'Thor Jun 5 '19 at 14:50
• @Randal'Thor My thinking was that it's supposed to read as a word: CHOPS – hexomino Jun 5 '19 at 14:53
• I didn’t want it to be obvious and also like hexoomino says, I needed a nice sounding word rather than random letters. – Uvc Jun 5 '19 at 15:09
• Without giving a spoiler, this distribution exhibits bias towards a certain, umm, planet... – smci Jun 6 '19 at 15:15
• @smci Unless you can name another planet with its own kind of <spoiler-redacted>, it's not really bias :) – chepner Jun 6 '19 at 17:25

N for Nitrogen

but let me take a stab at the title:

$$3^2 + 2^3 + 2^2 = 21$$; "guesses" more or less sounds as "gas is" so "21 gas is left". Air consists of 79% Nitrogen and 21% other gasses.

• Great find..but it is unintended correct coincidence..my reasoning was there are only 21 letters left..I just put it mathematically for fun.. – Uvc Jun 5 '19 at 15:28
• wow, almost seemed impossible to be a coincidence! – George Menoutis Jun 7 '19 at 8:45

This is a long shot, but the title could be a hint towards it.

W

because

3, 8, 15, 16, 19, 23, ... is the sequence of numbers whose base-5 representation contains no 2's and exactly one 3. (OEIS.)

• I heeded your suggestions and went non-mathematical for a change..title Is just a fancy way of expressing two neighbors. – Uvc Jun 5 '19 at 14:53
• Sometimes you wonder how such a sequence found its way to OEIS... – Evargalo Jun 5 '19 at 14:53
• @Evargalo Everything is on OEIS, I guess. – Rand al'Thor Jun 5 '19 at 14:54
• Not really..I developed more than 100 sequences specifically not to be found in oeis for mainly security management and cryptographic purposes. – Uvc Jun 5 '19 at 15:00
• @Uvc Huh??? All answers, including those about sequences, should be based on facts. – Rand al'Thor Jun 5 '19 at 15:13

According to the answer of hexomino I would say

N

Because

This is the writing order of chemical formula according to the Hill System, where atoms in molecules have to be named in this particular order.

• Right, but that's just a consequence (of the pattern mentioned by @hexomino et al.) rather than a cause. – smci Jun 6 '19 at 15:14