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 A293724 #20 Oct 16 2017 12:55:17 %S A293724 1,1,1,1,1,1,1,1,9,1,1,1,9,25,1,1,1,9,79,241,1,1,1,9,79,457,1041,1,1, %T A293724 1,9,79,841,5901,10681,1,1,1,9,79,841,7821,66841,60649,1,1,1,9,79,841, %U A293724 10821,118681,720259,658785,1,1,1,9,79,841,10821,136681,1782019 %N A293724 Square array A(n,k), n >= 0, k >= 1, read by antidiagonals, where column k is the expansion of e.g.f. exp(Sum_{j=1..k} j^2*x^j). %H A293724 Seiichi Manyama, <a href="/A293724/b293724.txt">Antidiagonals n = 0..139, flattened</a> %F A293724 A(0,k) = 1 and A(n,k) = (n-1)! * Sum_{j=1..min(k,n)} j^3*A(n-j,k)/(n-j)!. %e A293724 Square array begins: %e A293724 1, 1, 1, 1, 1, ... %e A293724 1, 1, 1, 1, 1, ... %e A293724 1, 9, 9, 9, 9, ... %e A293724 1, 25, 79, 79, 79, ... %e A293724 1, 241, 457, 841, 841, ... %e A293724 1, 1041, 5901, 7821, 10821, ... %Y A293724 Columns k=1..4 give A000012, A293720, A293721, A293723. %Y A293724 Rows n=0-1 give A000012. %Y A293724 Main diagonal gives A255807. %Y A293724 Cf. A293669, A293718. %K A293724 nonn,tabl %O A293724 0,9 %A A293724 _Seiichi Manyama_, Oct 15 2017