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Search: id:A151389
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| A151389 |
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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, 1), (0, -1), (1, 1)} |
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+0
1
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| 1, 0, 2, 2, 10, 22, 82, 220, 808, 2356, 8656, 26654, 98102, 312984, 1156032, 3782616, 14015132, 46756952, 173680748, 588380312, 2190211648, 7512444672, 28014835088, 97081546938, 362582983586, 1267349177760, 4739583478208, 16688334026768, 62482287911704, 221396939695828, 829766494964876, 2956346830527760
(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[i, 1 + j, -1 + n] + aux[1 + 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: A003609 A102446 A151456 this_sequence A151428 A102345 A151364
Adjacent sequences: A151386 A151387 A151388 this_sequence A151390 A151391 A151392
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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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