A148221 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, 0), (-1, 0, 1), (-1, 1, -1), (0, 1, 1), (1, -1, -1)}.

1, 1, 2, 4, 13, 31, 94, 288, 926, 2877, 9891, 33305, 114060, 398440, 1416214, 5011681, 18123463, 65923411, 241065146, 890520980, 3316802411, 12381311497, 46575028978, 176069708511, 667781099894, 2545534958577, 9747336415753, 37437157140905, 144427380938415, 559178373691931, 2170662589743925

Offset

0,3

Links

Table of n, a(n) for n=0..30.

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[i, -1 + j, -1 + k, -1 + n] + aux[1 + i, -1 + j, 1 + k, -1 + n] + aux[1 + i, j, -1 + k, -1 + n] + aux[1 + i, 1 + j, 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: A148218 A148219 A148220 * A148222 A148223 A148224

Adjacent sequences: A148218 A148219 A148220 * A148222 A148223 A148224

Keyword

nonn,walk

Author

Manuel Kauers, Nov 18 2008

Status

approved