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A151348
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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 n steps taken from {(-1, -1), (-1, 0), (-1, 1), (0, -1), (1, 0)}
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0
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1, 0, 1, 1, 4, 7, 25, 64, 201, 612, 1961, 6355, 21026, 70968, 241810, 837191, 2925393, 10334302, 36813216, 132242756, 478470272, 1742816732, 6387201912, 23539830561, 87207544029, 324627673245, 1213820275167, 4557447698656, 17177881979810, 64981216839823, 246648317043660, 939184339480746, 3586940782960596
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,5
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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, j, -1 + n] + aux[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, n], {n, 0, 25}]
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CROSSREFS
| Sequence in context: A079441 A129418 A073218 * A110413 A075686 A077441
Adjacent sequences: A151345 A151346 A151347 * A151349 A151350 A151351
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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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