%I A149247
%S A149247 1,1,4,11,38,116,440,1453,5530,18794,72792,257238,992644,3549594,13853496,
               50447453,196718714,
%T A149247 721500978,2829371848,10503154516,41147601932,153417689174,603530012488,
               2267966093122,
%U A149247 8917294536916,33615803655530,132535696401192,502544406495538,1980452388616776
%N A149247 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, 1, 0), 
               (1, 0, -1), (1, 1, 1)}
%H A149247 A. Bostan and M. Kauers, 2008. Automatic Classification of Restricted 
               Lattice Walks, <a href="http://arxiv.org/abs/0811.2899">ArXiv 0811.2899</
               a>.
%t A149247 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, 1 + k, -1 + n] + aux[1 + i, -1 + j, 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}]
%Y A149247 Sequence in context: A130494 A027573 A149246 this_sequence A149248 A149249 
               A149250
%Y A149247 Adjacent sequences: A149244 A149245 A149246 this_sequence A149248 A149249 
               A149250
%K A149247 nonn,walk
%O A149247 0,3
%A A149247 Manuel Kauers (manuel(AT)kauers.de), Nov 18 2008