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A151470 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, 0), (-1, 1), (0, 1), (1, 0), (1, 1)} 0
1, 1, 6, 18, 94, 386, 1979, 9262, 47785, 238604, 1246969, 6454615, 34187874, 180940665, 969918088, 5211150923, 28218545331, 153283951381, 837083867878, 4585637886067, 25219366928380, 139092895929290, 769504571196682, 4267822299499544, 23729769950773771, 132230104921510603, 738390549104421575 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..26.

M. Bousquet-Mélou and M. Mishna, 2008. Walks with small steps in the quarter plane, ArXiv 0810.4387.

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

CROSSREFS

Sequence in context: A194995 A104970 A216727 * A280096 A009573 A052655

Adjacent sequences:  A151467 A151468 A151469 * A151471 A151472 A151473

KEYWORD

nonn,walk

AUTHOR

Manuel Kauers, Nov 18 2008

STATUS

approved

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Last modified October 14 14:44 EDT 2019. Contains 328019 sequences. (Running on oeis4.)