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A151344 Number of walks within N^2 (the first quadrant of Z^2) starting and ending at (0,0) and consisting of 2 n steps taken from {(-1, -1), (-1, 0), (-1, 1), (1, -1), (1, 0)} 0
1, 1, 5, 35, 313, 3253, 37540, 467990, 6190709, 85835624, 1236484572, 18384929389, 280749914660, 4386014526625, 69882361534195, 1132723613672240, 18640032332057095, 310881221313870479, 5247411904749163561, 89530524469245596005, 1542486243771208605759, 26810622290131017450845 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..21.

M. Bousquet-Melou 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, j, -1 + n] + aux[-1 + 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[aux[0, 0, 2 n], {n, 0, 25}]

CROSSREFS

Sequence in context: A109253 A052797 A225177 * A015683 A000357 A102147

Adjacent sequences:  A151341 A151342 A151343 * A151345 A151346 A151347

KEYWORD

nonn,walk

AUTHOR

Manuel Kauers, Nov 18 2008

STATUS

approved

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Last modified April 21 01:47 EDT 2014. Contains 240824 sequences.