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 A209565 #7 Mar 30 2012 18:58:15 %S A209565 1,1,1,1,4,1,1,4,11,1,1,4,14,26,1,1,4,14,45,57,1,1,4,14,48,133,120,1, %T A209565 1,4,14,48,161,366,247,1,1,4,14,48,164,520,952,502,1,1,4,14,48,164, %U A209565 557,1604,2371,1013,1,1,4,14,48,164,560,1863,4724,5711,2036,1,1,4 %N A209565 Triangle of coefficients of polynomials u(n,x) jointly generated with A209566; see the Formula section. %C A209565 For a discussion and guide to related arrays, see A208510. %F A209565 u(n,x)=x*u(n-1,x)+v(n-1,x), %F A209565 v(n,x)=x*u(n-1,x)+2x*v(n-1,x)+1, %F A209565 where u(1,x)=1, v(1,x)=1. %e A209565 First five rows: %e A209565 1 %e A209565 1...1 %e A209565 1...4....1 %e A209565 1...4....11...1 %e A209565 1...4...14...26...1 %e A209565 First three polynomials v(n,x): 1, 1 + x, 1 + 4x + x^2. %t A209565 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A209565 u[n_, x_] := x*u[n - 1, x] + v[n - 1, x]; %t A209565 v[n_, x_] := x*u[n - 1, x] + 2 x*v[n - 1, x] + 1; %t A209565 Table[Expand[u[n, x]], {n, 1, z/2}] %t A209565 Table[Expand[v[n, x]], {n, 1, z/2}] %t A209565 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A209565 TableForm[cu] %t A209565 Flatten[%] (* A209565 *) %t A209565 Table[Expand[v[n, x]], {n, 1, z}] %t A209565 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A209565 TableForm[cv] %t A209565 Flatten[%] (* A209566 *) %Y A209565 Cf. A209566, A208510. %K A209565 nonn,tabl %O A209565 1,5 %A A209565 _Clark Kimberling_, Mar 10 2012