

A151295


Number of walks within N^2 (the first quadrant of Z^2) starting at (0,0) and consisting of n steps taken from {(1, 0), (0, 1), (0, 1), (1, 1), (1, 0)}


0



1, 2, 7, 24, 93, 364, 1490, 6178, 26163, 112001, 485272, 2120168, 9336512, 41376649, 184414880, 825963661, 3715457866, 16777860859, 76025036272, 345560464513, 1575102460028, 7197823974471, 32968875212361, 151333039522219, 696010343742969, 3206893602486167, 14800691952029228, 68415758808948051
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OFFSET

0,2


LINKS

Table of n, a(n) for n=0..27.
M. BousquetMÃ©lou and M. Mishna, 2008. Walks with small steps in the quarter plane, ArXiv 0810.4387.
A. Bostan and M. Kauers, 2008. Automatic Classification of Restricted Lattice Walks, ArXiv 0811.2899.


MATHEMATICA

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, j, 1 + n] + aux[1 + i, 1 + j, 1 + n] + aux[i, 1 + j, 1 + n] + aux[i, 1 + j, 1 + n] + aux[1 + i, j, 1 + n]]; Table[Sum[aux[i, j, n], {i, 0, n}, {j, 0, n}], {n, 0, 25}]


CROSSREFS

Sequence in context: A003041 A026558 A150402 * A150403 A150404 A150405
Adjacent sequences: A151292 A151293 A151294 * A151296 A151297 A151298


KEYWORD

nonn,walk,changed


AUTHOR

Manuel Kauers, Nov 18 2008


STATUS

approved



