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 A140189 #2 Mar 31 2012 10:31:22 %S A140189 1,1,2,3,7,9,16,22,42,57,90,124,204,275,413,562,866,1161,1685,2264, %T A140189 3308,4407 %N A140189 Number of groupoids (categories all of whose morphisms are invertible) with n morphisms. %C A140189 Row sums of A140188 (see comments and formula there). %Y A140189 Cf. A140185, A140188. %K A140189 nonn %O A140189 0,3 %A A140189 _Benoit Jubin_, May 12 2008