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 A290320 #7 Aug 04 2017 15:50:15
%S A290320 1,1,1,1,1,0,1,2,2,1,1,2,2,1,0,1,3,4,2,0,0,1,3,5,5,3,1,0,1,4,9,13,13,
%T A290320 9,4,1,1,4,9,13,13,9,4,1,0,1,5,14,25,30,24,12,3,0,0,1,5,15,30,42,42,
%U A290320 30,15,5,1,0,1,6,21,48,75,81,60,30,10,2,0,0
%N A290320 Write 1 - t * x/(1-x) as an inverse power product 1/(1+c(1)x) * 1/(1+c(2)x^2) * 1/(1+c(3)x^3) * ... The sequence is a regular triangle where T(n,k) is the coefficient of t^k in c(n), 1 <= k <= n.
%C A290320 An irregular triangle with only the nonzero coefficients is given by A290262.
%e A290320 Triangle begins:
%e A290320 1;
%e A290320 1, 1;
%e A290320 1, 1, 0;
%e A290320 1, 2, 2, 1;
%e A290320 1, 2, 2, 1, 0;
%e A290320 1, 3, 4, 2, 0, 0;
%e A290320 1, 3, 5, 5, 3, 1, 0;
%e A290320 1, 4, 9, 13, 13, 9, 4, 1;
%e A290320 1, 4, 9, 13, 13, 9, 4, 1, 0;
%e A290320 1, 5, 14, 25, 30, 24, 12, 3, 0, 0;
%e A290320 1, 5, 15, 30, 42, 42, 30, 15, 5, 1, 0;
%e A290320 1, 6, 21, 48, 75, 81, 60, 30, 10, 2, 0, 0;
%t A290320 nn=12;Solve[Table[Expand[SeriesCoefficient[Product[1/(1+c[k]x^k),{k,n}],{x,0,n}]]==-t,{n,nn}],Table[c[n],{n,nn}]][[1,All,2]]
%Y A290320 Cf. A220418, A273866, A289501, A290261, A290262.
%K A290320 nonn,tabl
%O A290320 1,8
%A A290320 _Gus Wiseman_, Jul 27 2017