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Search: id:A151410
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| A151410 |
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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, 0), (1, -1), (1, 0), (1, 1)} |
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+0
1
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| 1, 2, 10, 65, 490, 4032, 35244, 321750, 3035890, 29395652, 290621188, 2922898706, 29821640380, 307994453600, 3214454901480, 33855533036865, 359438259174930, 3843173300937300, 41351489731559700, 447450028715934090, 4866409456815200580, 53171146669028038560, 583400942149413843000
(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, j, -1 + n] + aux[-1 + i, 1 + j, -1 + n] + aux[1 + i, 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: A130721 A167449 A064170 this_sequence A027307 A060206 A108205
Adjacent sequences: A151407 A151408 A151409 this_sequence A151411 A151412 A151413
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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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