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 A210217 #4 Mar 30 2012 18:58:16 %S A210217 1,2,1,2,5,1,2,6,12,1,2,6,19,27,1,2,6,20,57,58,1,2,6,20,67,160,121,1, %T A210217 2,6,20,68,218,424,248,1,2,6,20,68,231,680,1073,503,1,2,6,20,68,232, %U A210217 775,2028,2619,1014,1,2,6,20,68,232,791,2543,5797,6214,2037,1,2 %N A210217 Triangle of coefficients of polynomials u(n,x) jointly generated with A210218; see the Formula section. %C A210217 Limiting row: A006012 %C A210217 Row sums: even-indexed Fibonacci numbers: 1,3,8,21,... %C A210217 For a discussion and guide to related arrays, see A208510. %F A210217 u(n,x)=x*u(n-1,x)+v(n-1,x)+1, %F A210217 v(n,x)=x*u(n-1,x)+2x*v(n-1,x)+1, %F A210217 where u(1,x)=1, v(1,x)=1. %e A210217 First five rows: %e A210217 1 %e A210217 2...1 %e A210217 2...5...1 %e A210217 2...6...12...1 %e A210217 2...6...19...27...1 %e A210217 First three polynomials u(n,x): 1, 2 + x, 2 + 5x + x^2. %t A210217 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A210217 u[n_, x_] := x*u[n - 1, x] + v[n - 1, x] + 1; %t A210217 v[n_, x_] := x*u[n - 1, x] + 2 x*v[n - 1, x] + 1; %t A210217 Table[Expand[u[n, x]], {n, 1, z/2}] %t A210217 Table[Expand[v[n, x]], {n, 1, z/2}] %t A210217 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A210217 TableForm[cu] %t A210217 Flatten[%] (* A210217 *) %t A210217 Table[Expand[v[n, x]], {n, 1, z}] %t A210217 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A210217 TableForm[cv] %t A210217 Flatten[%] (* A210218 *) %Y A210217 Cf. A210218, A208510. %K A210217 nonn,tabl %O A210217 1,2 %A A210217 _Clark Kimberling_, Mar 19 2012