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Search: id:A151423
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| A151423 |
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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 2 n steps taken from {(-1, -1), (-1, 0), (-1, 1), (1, -1), (1, 1)} |
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+0
1
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| 1, 3, 28, 355, 5264, 85764, 1488432, 27030861, 507976040, 9804514720, 193339562208, 3880220133244, 79026982569976, 1629698960355600, 33969388149210240, 714666181953790035, 15158444163422689080, 323839596100845917400, 6962822068346268247200, 150567286583848676406480
(list; graph; listen)
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OFFSET
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0,2
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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, 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[Sum[aux[0, k, 2 n], {k, 0, 2 n}], {n, 0, 25}]
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CROSSREFS
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Sequence in context: A076723 A026114 A072343 this_sequence A161605 A048954 A086569
Adjacent sequences: A151420 A151421 A151422 this_sequence A151424 A151425 A151426
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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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