# GUESS THE NEXT TERM!

## WHAT COMES NEXT AFTER:

Easy!     1, 1, 2, 3, 5, 8, 13, 21, 34, ?     Give up?

Pretty easy!     1, 1, 1, 3, 5, 9, 17, 31, 57, ?     Give up?

Easy! Fish in a big pond, perhaps?     1, 3, 7, 15, 31, 63, 127, 255, ?     Give up?

Still really easy!     1, 8, 11, 69, 88, 96, 101, 111, 181, 609, ?     Give up?

Classic, easy, supremely important:     2, 3, 5, 7, 11, 13, 17, 19, 23, 29, ?     Give up?

You knew they were not all going to be easy!     1, 2, 4, 6, 10, 12, 16, 18, 22, ?     Give up?

Those number sequences are all in the Online Encyclopedia of Integer Sequences (or OEIS).
But the real purpose of the OEIS is not puzzles, but identifying and
studying number sequences that have come up in people's work.

Here is a sequence that we are currently working on:
4   56   340   1120   3264     (Definition)
You won't be able to guess a formula, because no one in the world knows one!
Click the numbers to see gorgeous pictures of what we are counting (the number of regions).