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A151347
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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, 0), (-1, 1), (0, -1), (0, 1), (1, -1)}
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0
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1, 0, 1, 1, 3, 8, 19, 65, 177, 611, 1928, 6648, 22928, 80851, 292343, 1063611, 3957406, 14818681, 56339994, 215943994, 836246604, 3265240671, 12848804154, 50936668789, 203235590343, 816070826188, 3295317218038, 13379003847708, 54588942258042, 223782828113783, 921414594957514, 3809576782931810
(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, 1 + j, -1 + n] + aux[i, -1 + j, -1 + n] + aux[i, 1 + j, -1 + n] + aux[1 + i, -1 + j, -1 + n] + aux[1 + i, j, -1 + n]]; Table[aux[0, 0, n], {n, 0, 25}]
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CROSSREFS
| Sequence in context: A018032 A086808 A170900 * A047093 A060305 A009141
Adjacent sequences: A151344 A151345 A151346 * A151348 A151349 A151350
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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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