1,1

There are precisely 512 such numbers, see A009993.

a(1)=1, at n>1: a(n)=binomial(10, n)(1 - n/10)

a(2)=36 because there are 36 two-digit integers whose decimal digits are in increasing order (see A009993): 12, 13, 14, 15, 16, 17, 18, 19, 23, 24, 25, 26, 27, 28, 29, 34, 35, 36, 37, 38, 39, 45, 46, 47, 48, 49, 56, 57, 58, 59, 67, 68, 69, 78, 79, 89

Cf. A009993.

Sequence in context: A073613 A072517 A033585 this_sequence A050509 A118415 A051959

Adjacent sequences: A118626 A118627 A118628 this_sequence A118630 A118631 A118632

fini,full,nonn

Zak Seidov (zakseidov(AT)yahoo.com), May 09 2006