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 A173402 #6 Jan 05 2020 16:30:56 %S A173402 0,0,0,0,1,0,0,2,1,0,0,3,2,2,0,0,4,3,6,2,0,0,5,4,13,6,3,0,0,6,5,24,13, %T A173402 12,3,0,0,7,6,40,24,34,12,4,0,0,8,7,62,40,80,34,20,4,0,0,9,8,91,62, %U A173402 166,80,70,20,5,0,0,10,9,128,91,314,166,200,70,30,5,0 %N A173402 (A007318 - A112468)/2. %C A173402 Same as A131053, but with additional row/column of zeros. %e A173402 Array starts: %e A173402 0,0,0,0 %e A173402 0,1,1,2 %e A173402 0,2,2,6 %e A173402 0,3,3,13 %Y A173402 Cf. A007318, A112468, A131054, A131053. %K A173402 nonn,tabl %O A173402 1,8 %A A173402 _Mark Dols_, Feb 17 2010