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Search: id:A151426
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| A151426 |
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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), (-1, 0), (0, -1), (0, 1), (1, 0)} |
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+0
1
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| 1, 1, 3, 8, 25, 85, 291, 1072, 3949, 15143, 58563, 231111, 922494, 3724920, 15196256, 62498021, 259151683, 1081560013, 4542825176, 19184568461, 81432735810, 347241072470, 1486943756676, 6392073797253, 27576360268882, 119363438165113, 518246264053763, 2256543142841418, 9851632109402192
(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, j, -1 + n] + aux[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[Sum[aux[0, k, n], {k, 0, n}], {n, 0, 25}]
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CROSSREFS
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Sequence in context: A123638 A038665 A006372 this_sequence A045900 A000738 A148798
Adjacent sequences: A151423 A151424 A151425 this_sequence A151427 A151428 A151429
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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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