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 A220354 #8 Apr 17 2013 12:28:26 %S A220354 1,1,1,0,1,1,0,2,1,0,0,2,1,0,1,2,1,0,0,1,2,1,0,1,1,2,1,0,0,1,1,2,1,0, %T A220354 1,1,1,2,1,0,0,1,1,1,2,1,0,1,1,1,1,2,1,0,0,1,1,1,1,2,1,0,1,1,1,1,1,2, %U A220354 1,0,0,1,1,1,1,1,2,1,0,1,1,1,1,1,1,2,1 %N A220354 Irregular triangle T(n,k), read by rows; row n gives coefficients in expansion of P_n(x), which is defined by: P_0(x) = 1, P_n(x) = P_(n-1)(x)+x if n odd, P_n(x) = P_(n-1)(x)*x if n even. %C A220354 Row lengths are: 1, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, ... %F A220354 Sum_(T(n,k)*x^k, k>=0) = A019590(n+1), A008619(n+1), A123208(n) for x = 0, 1, 2 respectively. %e A220354 Irregular triangle begins: %e A220354 1 %e A220354 1, 1 %e A220354 0, 1, 1 %e A220354 0, 2, 1 %e A220354 0, 0, 2, 1 %e A220354 0, 1, 2, 1 %e A220354 0, 0, 1, 2, 1 %e A220354 0, 1, 1, 2, 1 %e A220354 0, 0, 1, 1, 2, 1 %e A220354 0, 1, 1, 1, 2, 1 %e A220354 0, 0, 1, 1, 1, 2, 1 %e A220354 0, 1, 1, 1, 1, 2, 1 %e A220354 0, 0, 1, 1, 1, 1, 2, 1 %e A220354 0, 1, 1, 1, 1, 1, 2, 1 %e A220354 ... %Y A220354 Cf. A219605. %K A220354 nonn,tabf %O A220354 0,8 %A A220354 _Philippe Deléham_, Apr 13 2013