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 A151383 #11 Dec 27 2023 21:31:32
%S A151383 1,3,18,135,1134,10206,96228,938223,9382230,95698746,991787004,
%T A151383 10413763542,110546105292,1184422556700,12791763612360,
%U A151383 139110429284415,1522031755700070,16742349312700770,185047018719324300,2054021907784499730,22887672686741568420,255925794588110265060
%N A151383 Number of walks within N^2 (the first quadrant of Z^2) starting at (0,0), ending on the vertical axis and consisting of 2 n steps taken from {(-1, -1), (-1, 0), (-1, 1), (1, 1)}.
%C A151383 Apparently a duplicate of A005159. [_R. J. Mathar_, Dec 13 2008]
%H A151383 M. Bousquet-Mélou and M. Mishna, <a href="http://arxiv.org/abs/0810.4387">Walks with small steps in the quarter plane</a>, arXiv:0810.4387 [math.CO], 2008-2009.
%t A151383 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[Sum[aux[0, k, 2 n], {k, 0, 2 n}], {n, 0, 25}]
%K A151383 nonn,walk
%O A151383 0,2
%A A151383 _Manuel Kauers_, Nov 18 2008