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 A108477 #9 Sep 05 2025 10:28:53
%S A108477 1,1,1,1,13,1,1,41,41,1,1,85,321,85,1,1,145,1289,1289,145,1,1,221,
%T A108477 3649,8989,3649,221,1,1,313,8361,40081,40081,8361,313,1,1,421,16641,
%U A108477 134245,265729,134245,16641,421,1,1,545,29961,369305,1256465,1256465,369305,29961,545,1
%N A108477 A symmetric number triangle based on 2^n.
%F A108477 T(n,k) = Sum_{j=0..n} C(2(n-k), j) * C(2k, j) * 2^j if 0<=k<=n otherwise 0.
%e A108477 Rows begin
%e A108477 1;
%e A108477 1, 1;
%e A108477 1, 13, 1;
%e A108477 1, 41, 41, 1;
%e A108477 1, 85, 321, 85, 1;
%e A108477 1, 145, 1289, 1289, 145, 1;
%Y A108477 Row sums are A108475.
%Y A108477 Diagonal sums are A108478.
%K A108477 easy,nonn,tabl,changed
%O A108477 0,5
%A A108477 _Paul Barry_, Jun 04 2005