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 A294250 #27 Oct 27 2017 11:01:08 %S A294250 1,1,0,1,1,0,1,1,1,0,1,1,3,1,0,1,1,3,13,1,0,1,1,3,19,49,1,0,1,1,3,19, %T A294250 97,261,1,0,1,1,3,19,121,681,1531,1,0,1,1,3,19,121,921,5971,9073,1,0, %U A294250 1,1,3,19,121,1041,8491,50443,63393,1,0,1,1,3,19,121,1041 %N A294250 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where column k is the expansion of e.g.f.: exp(Product_{j=1..n} (1+x^j) - 1). %H A294250 Seiichi Manyama, <a href="/A294250/b294250.txt">Antidiagonals n = 0..139, flattened</a> %F A294250 B(j,k) is the coefficient of Product_{i=1..k} (1+x^i). %F A294250 A(0,k) = 1 and A(n,k) = (n-1)! * Sum_{j=1..min(A000217(k),n)} j*B(j,k)*A(n-j,k)/(n-j)! for n > 0. %e A294250 Square array A(n,k) begins: %e A294250 1, 1, 1, 1, 1, ... %e A294250 0, 1, 1, 1, 1, ... %e A294250 0, 1, 3, 3, 3, ... %e A294250 0, 1, 13, 19, 19, ... %e A294250 0, 1, 49, 97, 121, ... %e A294250 0, 1, 261, 681, 921, ... %Y A294250 Columns k=0..5 give A000007, A000012, A118589, A294251, A294252, A294253. %Y A294250 Rows n=0 gives A000012. %Y A294250 Main diagonal gives A293840. %Y A294250 Cf. A070936, A294212, A294254. %K A294250 nonn,tabl %O A294250 0,13 %A A294250 _Seiichi Manyama_, Oct 26 2017