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 A202690 #20 Jun 03 2020 03:45:39
%S A202690 1,1,0,1,1,2,4,4,3,3,2,0,0,4,8,11,11,14,16,16,80,80,76,68,57,57,46,32,
%T A202690 16,0,0,80,160,236,304,361,361,418,464,496,512,512,3904,3904,3824,
%U A202690 3664,3428,3124,2763,2763,2402,1984,1520,1024,512,0
%N A202690 The triangle in A185356 with the central column of zeros omitted.
%H A202690 M. Josuat-Vergès, J.-C. Novelli and J.-Y. Thibon, <a href="http://arxiv.org/abs/1110.5272">The algebraic combinatorics of snakes</a>, arXiv preprint arXiv:1110.5272 [math.CO], 2011.
%e A202690 Triangle begins:
%e A202690 1 1
%e A202690 0 1 1 2
%e A202690 4 4 3 3 2 0
%e A202690 0 4 8 11 11 14 16 16
%e A202690 80 80 76 68 57 57 46 32 16 0
%e A202690 0 80 160 236 304 361 361 418 464 496 512 512
%o A202690 (PARI) T(n,k) = {if ((k==0), return(0)); if (n==1, if (abs(k)==1, return(1))); if (n%2, if (k<0, sum(j=k+1, n-1, T(n-1,j)), sum(j=k, n-1, T(n-1,j))), if (k<0, sum(j=-n+1, k, T(n-1,j)), sum(j=-n+1, k-1, T(n-1,j))));}
%o A202690 tabf(nn) = {for (n=1, nn, for (k=-n, n, if (k, print1(T(n, k), ", "));); print;);} \\ _Michel Marcus_, Jun 03 2020
%Y A202690 Cf. A185356, A202691, A202704.
%K A202690 nonn,tabf
%O A202690 1,6
%A A202690 _N. J. A. Sloane_, Dec 22 2011
%E A202690 More terms from _Michel Marcus_, Jun 03 2020