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 A061897 #9 Nov 18 2022 03:39:16 %S A061897 1,0,2,0,0,2,0,0,4,2,0,0,8,6,2,0,0,16,18,8,2,0,0,32,54,28,10,2,0,0,64, %T A061897 162,96,40,12,2,0,0,128,486,328,150,54,14,2,0,0,256,1458,1120,550,220, %U A061897 70,16,2,0,0,512,4374,3824,2000,858,308,88,18,2,0,0,1024,13122,13056 %N A061897 Square table by antidiagonals of number of routes of length 2k+n on the sides of a 2n-gon from a point to its opposite point. %F A061897 T(0, 0)=1; if n>0, T(n, 0)=2; if k>1, T(n, k)=T(n, k-1)*A061896(n, 1)-T(n, k-2)*A061896(n, 2)+T(n, k-3)*A061896(n, 3)-T(n, k-4)*A061896(n, 4)+...T(n, k-[n/2])*A061896(n, [n/2]); if 0>k T(n, k)=0. %e A061897 Rows start %e A061897 1, 0, 0, 0, 0, ... %e A061897 2, 0, 0, 0, 0, ... %e A061897 2, 4, 8, 16, 32, ... %e A061897 2, 6, 18, 54, 162, ... %e A061897 2, 8, 28, 96, 328, ... %e A061897 ... %Y A061897 Cf. A060995. Rows include A000007, A000038, A000079, A008776, A060995. Columns effectively (i.e. except for a small number of terms) include A040000, A005843, A028552. %K A061897 nonn,tabl %O A061897 0,3 %A A061897 _Henry Bottomley_, May 14 2001