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Search: id:A151400
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| A151400 |
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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, 0), (-1, 1), (0, -1), (1, 1)} |
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+0
1
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| 1, 0, 2, 4, 10, 32, 108, 312, 1036, 3552, 11680, 39214, 136772, 471748, 1626866, 5722264, 20199400, 71116826, 252507746, 902188304, 3222655648, 11548005134, 41588468526, 150008189222, 541865647164, 1963642984244, 7131101379546, 25927597277242, 94455538469920, 344779963787714, 1260046402628588
(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, 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: A005268 A005269 A070900 this_sequence A071954 A120017 A000736
Adjacent sequences: A151397 A151398 A151399 this_sequence A151401 A151402 A151403
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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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