# A Harry Potter sequence puzzle

What is the next term in the following sequence based on Harry Potter?

None, 16, None, 16, 5, 9, ?

The next term in the sequence is:

22

Because:

These are the chapter numbers which share their name with the part of the book title that follows 'Harry Potter and...' (in order of the books' publication):

Book 1 - none: no chapter called 'The Philosopher's Stone';
Book 2 - Chapter 16: 'The Chamber of Secrets';
Book 3 - none: no chapter called 'The Prisoner of Azkaban';
Book 4 - Chapter 16: 'The Goblet of Fire';
Book 5 - Chapter 5: 'The Order of the Phoenix';
Book 6 - Chapter 9: 'The Half-Blood Prince';
Book 7 - Chapter 22: 'The Deathly Hallows'.

EDIT: Since some commenters wish to understand the thought process behind my solving this puzzle, here's roughly how I approached it:

1) There are 7 terms in the sequence, and there are 7 HP books - let's assume that each term in the sequence maps to one of the books...

2) Why are the two null entries written as 'None' rather than '0'? This probably means we're not counting something, otherwise the OP would have just used a zero character;

3) What other numbers are relevant to books - chapter numbers, to start...

4) Look up the chapters of these numbers in the relevant books;

5) GASP AS YOU SPOT THE CONNECTION!!

• @MalachiHolden there are a few hints that would point you in certain directions. First hint is that there are 6 given answers, and they're asking you for the 7 one. If you're familiar with Harry Potter, you know there are 7 books, so there's a good chance the puzzle is a 1 answer per book type of puzzle. – TKoL Jul 22 at 16:56
• @MalachiHolden then you do the same with chapters, and the answer jumps out at you. – TKoL Jul 22 at 16:57
• @MalachiHolden My rough thought process was: 1) There are 7 terms in the sequence, and there are 7 HP books - let's assume that each term in the sequence maps to one of the books... 2) Why are the two null entries written as 'None' rather than '0'? This probably means we're not counting something, otherwise the OP would have just used a zero character; 3) What other numbers are relevant to books - chapter numbers... 4) Look up the chapters of these numbers in the relevant books; 5) GASP AS YOU SPOT THE CONNECTION!! – Stiv Jul 22 at 17:03
• @Stiv: You should edit that into your answer! I am firmly of the belief that good answers on this site explain not just the answer but how you got there too! Its a shame to leave such valuable information in comments! – Chris Jul 23 at 11:05
• @Chris Agreed, and answer updated accordingly :) – Stiv Jul 23 at 11:28