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 A151343 #9 Dec 27 2023 21:37:24
%S A151343 1,1,4,29,230,2034,19636,200219,2128690,23402066,264236768,3049648298,
%T A151343 35848893160,428019644312,5179187934336,63402498105619,
%U A151343 784107314998826,9784873540094834,123088167713040424,1559540214271770126,19887838197050534036,255108227918077438572,3289865618218314784376
%N A151343 Number of walks within N^2 (the first quadrant of Z^2) starting and ending at (0,0) and consisting of 2 n steps taken from {(-1, -1), (-1, 0), (1, -1), (1, 1)}.
%H A151343 A. Bostan, K. Raschel, B. Salvy, <a href="http://dx.doi.org/10.1016/j.jcta.2013.09.005">Non-D-finite excursions in the quarter plane</a>, J. Comb. Theory A 121 (2014) 45-63, Table 1 Tag 7, Tag 17.
%H A151343 M. Bousquet-Mélou and M. Mishna, 2008. Walks with small steps in the quarter plane, <a href="http://arxiv.org/abs/0810.4387">ArXiv 0810.4387</a>.
%t A151343 aux[i_Integer, j_Integer, n_Integer] := Which[Min[i, j, n] < 0 || Max[i, j] > n, 0, n == 0, KroneckerDelta[i, j, n], True, aux[i, j, n] = aux[-1 + i, -1 + j, -1 + n] + aux[-1 + i, 1 + j, -1 + n] + aux[1 + i, j, -1 + n] + aux[1 + i, 1 + j, -1 + n]]; Table[aux[0, 0, 2 n], {n, 0, 25}]
%K A151343 nonn,walk
%O A151343 0,3
%A A151343 _Manuel Kauers_, Nov 18 2008