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 A209143 #7 Mar 30 2012 18:58:15 %S A209143 1,2,1,5,4,11,11,1,23,28,6,47,68,23,1,95,160,74,8,191,368,216,39,1, %T A209143 383,832,592,152,10,767,1856,1552,520,59,1,1535,4096,3936,1632,270,12, %U A209143 3071,8960,9728,4816,1060,83,1,6143,19456,23552,13568,3752,436 %N A209143 Triangle of coefficients of polynomials u(n,x) jointly generated with A209144; see the Formula section. %C A209143 Alternating row sums: 1,1,1,1,1,1,1,1,1,1,1,1,1,... %C A209143 For a discussion and guide to related arrays, see A208510. %F A209143 u(n,x)=u(n-1,x)+(x+1)*v(n-1,x), %F A209143 v(n,x)=u(n-1,x)+v(n-1,x) + 1, %F A209143 where u(1,x)=1, v(1,x)=1. %e A209143 First five rows: %e A209143 1 %e A209143 2....1 %e A209143 5....4 %e A209143 11...11...1 %e A209143 23...28...6 %e A209143 First three polynomials u(n,x): 1, 2 + x, 5 + 4x %t A209143 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A209143 u[n_, x_] := u[n - 1, x] + (x + 1)*v[n - 1, x]; %t A209143 v[n_, x_] := u[n - 1, x] + v[n - 1, x] + 1; %t A209143 Table[Expand[u[n, x]], {n, 1, z/2}] %t A209143 Table[Expand[v[n, x]], {n, 1, z/2}] %t A209143 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A209143 TableForm[cu] %t A209143 Flatten[%] (* A209143 *) %t A209143 Table[Expand[v[n, x]], {n, 1, z}] %t A209143 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A209143 TableForm[cv] %t A209143 Flatten[%] (* A209144 *) %Y A209143 Cf. A209144, A208510. %K A209143 nonn,tabf %O A209143 1,2 %A A209143 _Clark Kimberling_, Mar 06 2012