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 A210225 #4 Mar 30 2012 18:58:16 %S A210225 1,2,1,3,5,1,4,12,10,1,5,22,36,17,1,6,35,88,87,26,1,7,51,175,277,181, %T A210225 37,1,8,70,306,680,734,338,50,1,9,92,490,1416,2196,1710,582,65,1,10, %U A210225 117,736,2632,5402,6156,3606,941,82,1,11,145,1053,4502,11592 %N A210225 Triangle of coefficients of polynomials u(n,x) jointly generated with A210226; see the Formula section. %C A210225 For a discussion and guide to related arrays, see A208510. %F A210225 u(n,x)=x*u(n-1,x)+v(n-1,x)+1, %F A210225 v(n,x)=2x*u(n-1,x)+(x+1)*v(n-1,x)+1, %F A210225 where u(1,x)=1, v(1,x)=1. %e A210225 First five rows: %e A210225 1 %e A210225 2...1 %e A210225 3...5....1 %e A210225 4...12...10...1 %e A210225 5...22...36...17...1 %e A210225 First three polynomials u(n,x): 1, 2 + x, 3 + 5x + x^2. %t A210225 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A210225 u[n_, x_] := x*u[n - 1, x] + v[n - 1, x] + 1; %t A210225 v[n_, x_] := 2 x*u[n - 1, x] + (x + 1)*v[n - 1, x] + 1; %t A210225 Table[Expand[u[n, x]], {n, 1, z/2}] %t A210225 Table[Expand[v[n, x]], {n, 1, z/2}] %t A210225 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A210225 TableForm[cu] %t A210225 Flatten[%] (* A210225 *) %t A210225 Table[Expand[v[n, x]], {n, 1, z}] %t A210225 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A210225 TableForm[cv] %t A210225 Flatten[%] (* A210226 *) %Y A210225 Cf. A210226, A208510. %K A210225 nonn,tabl %O A210225 1,2 %A A210225 _Clark Kimberling_, Mar 20 2012