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A151353
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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), (0, -1), (1, 1)}
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0
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1, 0, 1, 2, 2, 14, 21, 76, 252, 566, 2282, 6248, 19958, 69356, 205129, 720868, 2340178, 7692570, 26681224, 87814024, 302838250, 1035805496, 3526054994, 12286338876, 42255768876, 147090631152, 513835481206, 1790785075144, 6298459417432, 22120204885156, 77965202090697, 275780508039312, 975587671958542
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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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[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: A032209 A032134 A032038 * A151437 A194689 A166114
Adjacent sequences: A151350 A151351 A151352 * A151354 A151355 A151356
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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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