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 A210200 #5 Mar 30 2012 18:58:16 %S A210200 1,2,2,4,5,2,7,12,7,2,12,25,21,9,2,20,50,53,32,11,2,33,96,124,94,45, %T A210200 13,2,54,180,273,250,150,60,15,2,88,331,577,617,445,223,77,17,2,143, %U A210200 600,1181,1444,1212,728,315,96,19,2,232,1075,2358,3242,3101,2163 %N A210200 Triangle of coefficients of polynomials v(n,x) jointly generated with A210199; see the Formula section. %C A210200 Alternating row sums: 1,0,1,0,1,0,1,0,1,0,... %C A210200 For a discussion and guide to related arrays, see A208510. %F A210200 u(n,x)=u(n-1,x)+v(n-1,x)+1, %F A210200 v(n,x)=(x+1)*u(n-1,x)+x*v(n-1,x)+1, %F A210200 where u(1,x)=1, v(1,x)=1. %e A210200 First five rows: %e A210200 1 %e A210200 2....2 %e A210200 4....5....2 %e A210200 7....12...7....2 %e A210200 12...25...21...9...2 %e A210200 First three polynomials v(n,x): 1, 2 + 2x , 4 + 5x + 2x^2. %t A210200 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A210200 u[n_, x_] := u[n - 1, x] + v[n - 1, x] + 1; %t A210200 v[n_, x_] := (x + 1)*u[n - 1, x] + x*v[n - 1, x] + 1; %t A210200 Table[Expand[u[n, x]], {n, 1, z/2}] %t A210200 Table[Expand[v[n, x]], {n, 1, z/2}] %t A210200 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A210200 TableForm[cu] %t A210200 Flatten[%] (* A210199 *) %t A210200 Table[Expand[v[n, x]], {n, 1, z}] %t A210200 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A210200 TableForm[cv] %t A210200 Flatten[%] (* A210200 *) %Y A210200 Cf. A210199, A208510. %K A210200 nonn,tabl %O A210200 1,2 %A A210200 _Clark Kimberling_, Mar 18 2012