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A151358
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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, -1), (1, 0)}
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0
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1, 0, 1, 3, 7, 29, 101, 404, 1657, 6987, 30666, 136679, 624485, 2899186, 13670079, 65344840, 316012215, 1544872132, 7624022772, 37951505458, 190398999412, 962031788591, 4892669207705, 25032214282235, 128780148586223, 665906668042143, 3459650667634130, 18053515979281908, 94595985460340024
(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, j, -1 + n] + aux[-1 + i, 1 + 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: A148766 A148767 A171180 * A110613 A088095 A173280
Adjacent sequences: A151355 A151356 A151357 * A151359 A151360 A151361
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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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