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A151361
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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, 0), (1, 1)}
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0
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1, 2, 13, 124, 1427, 18424, 257090, 3794091, 58411957, 929535968, 15190791558, 253735278108, 4316305707838, 74571507312612, 1305616160300541, 23124883139330156, 413757060245969804, 7469673227755295934, 135931742489359394834, 2491396081566293784574, 45957915237430642944461
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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LINKS
| M. Bousquet-Melou and M. Mishna, 2008. Walks with small steps in the quarter plane, ArXiv 0810.4387.
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MATHEMATICA
| 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, 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}]
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CROSSREFS
| Sequence in context: A192460 A004122 A086630 * A073559 A074365 A071362
Adjacent sequences: A151358 A151359 A151360 * A151362 A151363 A151364
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KEYWORD
| nonn,walk
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AUTHOR
| Manuel Kauers (manuel(AT)kauers.de), Nov 18 2008
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