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Search: id:A151445
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| A151445 |
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Number of walks within N^2 (the first quadrant of Z^2) starting at (0,0), ending on the vertical axis and consisting of n steps taken from {(-1, -1), (0, 1), (1, -1), (1, 0), (1, 1)} |
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+0
1
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| 1, 1, 2, 6, 16, 49, 165, 538, 1881, 6673, 23954, 87931, 326739, 1224662, 4649697, 17778696, 68513483, 265907818, 1038089219, 4074688736, 16076107171, 63703583554, 253492204031, 1012528480799, 4058431546038, 16319598817463, 65820404923113, 266202737052052, 1079421216584541, 4387508855164279
(list; graph; listen)
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OFFSET
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0,3
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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, -1 + j, -1 + 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]]; Table[Sum[aux[0, k, n], {k, 0, n}], {n, 0, 25}]
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CROSSREFS
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Sequence in context: A079565 A052890 A052814 this_sequence A000136 A013989 A002841
Adjacent sequences: A151442 A151443 A151444 this_sequence A151446 A151447 A151448
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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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