Continue in a clockwise direction
910 is the generalized Catalan number C(11,4).
Catalan number 4x4 grid example.svg
The Catalan numbers give the number of ways to tile an n-sized stair case with exactly n rectangles.
An Introduction to Catalan Numbers ( Compact Textbooks in Mathematics) (Hardcover)
Not the last application of Catalan Numbers, but the most interesting IMO
Math Encounters -- A Surreptitious Sequence: The Catalan Numbers