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 A059510 #7 Sep 11 2017 02:55:46
%S A059510 1,1,8,152,4493,202066,12841750,1097043147,121284672716,
%T A059510 16850062144162,2873723485196575,590279507847844136,
%U A059510 143737044733324878879,40943428029694983816963,13488163010054730357533318,5088553275271661089776406989
%N A059510 Main diagonal of the array A059220.
%H A059510 G. C. Greubel, <a href="/A059510/b059510.txt">Table of n, a(n) for n = 1..240</a>
%t A059510 t[0, 0] = 1; t[0, _?EvenQ] = 0; t[_?OddQ, 0] = 0; t[n_, k_] /; OddQ[n + k] (*up*):= t[n, k] = t[n + 1, k - 1] + Sum[t[n, j], {j, 0, k - 1}];
%t A059510 t[n_, k_] /; EvenQ[n + k] (*down*):= t[n, k] = t[n - 1, k + 1] + Sum[t[j, k], {j, 0, n - 1}]; Table[t[n, n], {n,0,50}] (* _G. C. Greubel_, Sep 10 2017 *)
%K A059510 easy,nonn
%O A059510 1,3
%A A059510 _Floor van Lamoen_, Jan 21 2001
%E A059510 Terms a(11) onward added by _G. C. Greubel_, Sep 10 2017