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 A208508 #10 Nov 07 2015 13:57:40 %S A208508 1,1,1,1,4,1,9,1,1,16,6,1,25,20,1,1,36,50,8,1,49,105,35,1,1,64,196, %T A208508 112,10,1,81,336,294,54,1,1,100,540,672,210,12,1,121,825,1386,660,77, %U A208508 1,1,144,1210,2640,1782,352,14,1,169,1716,4719,4290,1287,104,1,1 %N A208508 Triangle of coefficients of polynomials u(n,x) jointly generated with A208509; see the Formula section. %C A208508 col 1: A000012 %C A208508 col 2: A000290 (squares) %C A208508 col 3: A002415 %C A208508 col 4: A040977 %C A208508 col 5: A054334 %C A208508 row sums, u(n,1): A083329 %F A208508 u(n,x)=u(n-1,x)+x*v(n-1,x), %F A208508 v(n,x)=u(n-1,x)+v(n-1,x)+1, %F A208508 where u(1,x)=1, v(1,x)=1. %e A208508 First five rows: %e A208508 1 %e A208508 1...1 %e A208508 1...4 %e A208508 1...9....1 %e A208508 1...16...6 %e A208508 First five polynomials u(n,x): %e A208508 1 %e A208508 1 + x %e A208508 1 + 4x %e A208508 1 + 9x + x^2 %e A208508 1 + 16x + 6x^2 %t A208508 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A208508 u[n_, x_] := u[n - 1, x] + x*v[n - 1, x]; %t A208508 v[n_, x_] := u[n - 1, x] + v[n - 1, x] + 1; %t A208508 Table[Expand[u[n, x]], {n, 1, z/2}] %t A208508 Table[Expand[v[n, x]], {n, 1, z/2}] %t A208508 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A208508 TableForm[cu] %t A208508 Flatten[%] (* A208508 *) %t A208508 Table[Expand[v[n, x]], {n, 1, z}] %t A208508 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A208508 TableForm[cv] %t A208508 Flatten[%] (* A208509 *) %Y A208508 Cf. A208509. %K A208508 nonn,tabf %O A208508 1,5 %A A208508 _Clark Kimberling_, Feb 27 2012