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A149924 Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 1), (-1, 0, 0), (0, 1, 0), (1, 0, 0), (1, 1, -1)} 0
1, 2, 5, 15, 47, 161, 580, 2167, 8409, 33338, 135326, 558608, 2341146, 9943026, 42693924, 185206211, 810338935, 3573667942, 15869799860, 70918166895, 318720501038, 1439761710718, 6534533849551, 29784956742499, 136299263675179, 625984572847841, 2884631908757017, 13334144847813943 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..27.

A. Bostan and M. Kauers, 2008. Automatic Classification of Restricted Lattice Walks, ArXiv 0811.2899.

MATHEMATICA

aux[i_Integer, j_Integer, k_Integer, n_Integer] := Which[Min[i, j, k, n] < 0 || Max[i, j, k] > n, 0, n == 0, KroneckerDelta[i, j, k, n], True, aux[i, j, k, n] = aux[-1 + i, -1 + j, 1 + k, -1 + n] + aux[-1 + i, j, k, -1 + n] + aux[i, -1 + j, k, -1 + n] + aux[1 + i, j, k, -1 + n] + aux[1 + i, 1 + j, -1 + k, -1 + n]]; Table[Sum[aux[i, j, k, n], {i, 0, n}, {j, 0, n}, {k, 0, n}], {n, 0, 10}]

CROSSREFS

Sequence in context: A192053 A149923 A219231 * A149925 A149926 A321467

Adjacent sequences:  A149921 A149922 A149923 * A149925 A149926 A149927

KEYWORD

nonn,walk

AUTHOR

Manuel Kauers, Nov 18 2008

STATUS

approved

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Last modified October 20 07:41 EDT 2020. Contains 337897 sequences. (Running on oeis4.)