This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A217210 #4 Oct 01 2012 12:34:36 %S A217210 0,1,2,5,9,18,34,71,139,280,555,1119,2228,4462,8907,17835,35634,71288, %T A217210 142507,285077,570013,1140102,2279924,4560040,9119516,18239335, %U A217210 36477548,72955801,145909351,291819915,583635336,1167273283 %N A217210 Number of strings of n 2's and 3's having a tail of length 1. %Y A217210 This is the k=1 column (the second column) of the triangle in A217209. %K A217210 nonn %O A217210 1,3 %A A217210 _N. J. A. Sloane_, Oct 01 2012