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Search: id:A151415
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| A151415 |
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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, 0), (1, 1)} |
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+0
1
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| 1, 0, 2, 3, 10, 27, 89, 267, 868, 2858, 9510, 31830, 108638, 373219, 1288064, 4482534, 15710368, 55258931, 195240700, 693284513, 2470263132, 8827776270, 31654190580, 113835950410, 410335021648, 1482638356348, 5369592056146, 19484896375080, 70835100481126, 257981797359638, 941120763934455, 3438343699103345
(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[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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Adjacent sequences: A151412 A151413 A151414 this_sequence A151416 A151417 A151418
Sequence in context: A005158 A005225 A052929 this_sequence A134588 A000060 A089752
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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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