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 A209158 #5 Mar 30 2012 18:58:15 %S A209158 1,2,1,3,5,3,4,11,13,5,5,19,35,31,11,6,29,73,101,73,21,7,41,131,247, %T A209158 275,167,43,8,55,213,509,769,717,377,85,9,71,323,935,1787,2255,1811, %U A209158 839,171,10,89,465,1581,3657,5829,6321,4461,1849,341,11,109,643 %N A209158 Triangle of coefficients of polynomials u(n,x) jointly generated with A209159; see the Formula section. %C A209158 Alternating row sums: 1,1,1,1,1,1,1,1,1,1,1,1,1,1,... %C A209158 For a discussion and guide to related arrays, see A208510. %F A209158 u(n,x)=u(n-1,x)+(x+1)*v(n-1,x), %F A209158 v(n,x)=2x*u(n-1,x)+x*v(n-1,x)+1, %F A209158 where u(1,x)=1, v(1,x)=1. %e A209158 First five rows: %e A209158 1 %e A209158 2...1 %e A209158 3...5....5 %e A209158 4...11...13...5 %e A209158 5...19...35...31...11 %e A209158 First three polynomials v(n,x): 1, 2 + x, 3 + 5x + 5x^2. %t A209158 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A209158 u[n_, x_] := u[n - 1, x] + (x + 1)*v[n - 1, x]; %t A209158 v[n_, x_] := 2 x*u[n - 1, x] + x*v[n - 1, x] + 1; %t A209158 Table[Expand[u[n, x]], {n, 1, z/2}] %t A209158 Table[Expand[v[n, x]], {n, 1, z/2}] %t A209158 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A209158 TableForm[cu] %t A209158 Flatten[%] (* A209158 *) %t A209158 Table[Expand[v[n, x]], {n, 1, z}] %t A209158 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A209158 TableForm[cv] %t A209158 Flatten[%] (* A209159 *) %Y A209158 Cf. A209159, A208510. %K A209158 nonn,tabl %O A209158 1,2 %A A209158 _Clark Kimberling_, Mar 07 2012