a(1) = 1, a(n) = smallest positive number b not among a(1)..a(n-1) and not a multiple of 10 such that the first digit of b = the last digit of a(n-1).
1, 11, 12, 21, 13, 31, 14, 41, 15, 51, 16, 61, 17, 71, 18, 81, 19, 91, 101, 102, 22, 23
3 seqfan posts
Thu Jan 29 12:57:05 CET 2009 [seqfan] Re: Starting and Ending Digits