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Search: id:A151352
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| A151352 |
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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, 0)} |
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+0
1
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| 1, 0, 1, 2, 2, 13, 21, 67, 231, 509, 1947, 5522, 16637, 58030, 170547, 579290, 1896475, 6081303, 20884509, 68398930, 231286693, 788124656, 2649341358, 9130259705, 31203913903, 107304612514, 372144639423, 1285741209096, 4480102404983, 15625089552273, 54591352088818, 191664831925204, 673088362068478
(list; graph; listen)
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OFFSET
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0,4
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LINKS
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M. Bouquet-Melou and M. Mishna, 2008. Walks with small steps in the quarter plane, ArXiv 0810.4387.
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MATHEMATICA
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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, j, -1 + n] + aux[1 + i, 1 + j, -1 + n]]; Table[aux[0, 0, n], {n, 0, 25}]
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CROSSREFS
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Sequence in context: A130718 A074477 A141575 this_sequence A155915 A151367 A057648
Adjacent sequences: A151349 A151350 A151351 this_sequence A151353 A151354 A151355
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KEYWORD
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nonn,walk
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AUTHOR
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Manuel Kauers (manuel(AT)kauers.de), Nov 18 2008
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