Here are three different letter/number sequences. Try to solve as many as possible. The spoilers give hints to each sequence in the form of how many elements are in the corresponding sequence.

Sequence 1 (Missing Elements: 2) [Solved by xnor]

Y, Y, ?, L, Y, E, ?, T, R...

There are 12 elements in this sequence.

Sequence 2 (Missing Elements: 2) [Solved by Tryth]

a, H, R, 0, c, ?, o, ?, L, 3, B...

There are 44 elements in this sequence.

Sequence 3 (Missing Elements: 3) [Solved by finsternis]

?, P, C, P, C, ?, B, R, B, R, ?, R, S, R, S, R...

There are 29 elements in this sequence.

The first one is quite simple but the other two are fairly challenging. Good luck!

  • $\begingroup$ 2 and 3 are really tough one, spend around 1 hour to analyse country group, country/capital group for puzzle 3, no result so far. Taking time out. $\endgroup$ Commented Mar 25, 2015 at 6:08
  • $\begingroup$ Why didn't you ask this as three separate questions? $\endgroup$
    – not my job
    Commented Mar 25, 2015 at 17:15
  • $\begingroup$ @enoughreptocomment now that I see how difficult the last one is, I would consider it but that is something I never thought of doing at first. $\endgroup$
    – GamrCorps
    Commented Mar 25, 2015 at 18:00
  • $\begingroup$ Sequence 3 is currently the sixth most famous 29-element sequence on the internet - well done! $\endgroup$ Commented Mar 26, 2015 at 1:21
  • $\begingroup$ @randal'thor Thanks! I'm honesty surprised that no one has guessed it by now. $\endgroup$
    – GamrCorps
    Commented Mar 26, 2015 at 4:04

3 Answers 3


Sequence 3:

Order of speakers in Shakespeare's Romeo and Juliet Act I, Scene ii:
Capulet, Paris, Capulet, ...
The full sequence is C, P, C, P, C, S, B, R, B, R, B, R, S, R, S, R, S, R, S, R, S, R, S, R, S, B, R, B, R
and the missing elements are C, S, and B. (S = Peter the servant)

  • 3
    $\begingroup$ WOW! How on earth did you manage to solve this? Really impressive. $\endgroup$ Commented Mar 28, 2015 at 10:59
  • 1
    $\begingroup$ Bravo! Out of curiosity, did you use my hint? $\endgroup$
    – GamrCorps
    Commented Mar 28, 2015 at 13:53
  • $\begingroup$ Yes, the hint really helped! $\endgroup$
    – finsternis
    Commented Mar 29, 2015 at 3:20

Sequence 2:

This represents the base64 encoded form of the string http://puzzling.stackexchange.com. This corresponds to aHR0cDovL3B1enpsaW5nLnN0YWNrZXhjaGFuZ2UuY29t. Therefore the missing elements are D and v.

  • $\begingroup$ I did not expect anyone to get that so fast. Good job! $\endgroup$
    – GamrCorps
    Commented Mar 25, 2015 at 14:24
  • $\begingroup$ Can you post your method for how you solved this? Did something point you to base64 encodings? $\endgroup$ Commented Jan 4, 2016 at 16:53
  • $\begingroup$ @user1717828 When I see mixed uppercase, lowercase and numbers base64 is usually my first guess. $\endgroup$
    – Tryth
    Commented Jan 6, 2016 at 2:48

Sequence 1:

Last letters of months:
January, February, March, April, May, June, July, August, September, October, November, December
which gives the sequence Y, Y, H, L, Y, E, Y, T, R, R, R, R.
The missing elements are H and Y.

  • $\begingroup$ I was just about to post this, lol. $\endgroup$
    – user88
    Commented Mar 25, 2015 at 5:22

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