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A151351
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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, 1)}
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0
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1, 0, 1, 1, 8, 18, 90, 301, 1413, 5628, 26083, 114133, 536065, 2475101, 11844488, 56598072, 275910093, 1350392157, 6692423872, 33348850521, 167631991925, 847255772901, 4310527391729, 22040709981279, 113295384193957, 584965125869980, 3033583060169821, 15793448306316644, 82532818466952627
(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[-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: A032795 A120543 A036747 * A113563 A173734 A171371
Adjacent sequences: A151348 A151349 A151350 * A151352 A151353 A151354
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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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