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 A277262 Number of walks on cubic lattice starting at (1,1,1), ending at (n,n,n), remaining in the first (nonnegative) octant and using steps (0,-1,2), (0,2,-1), (-1,0,2), (2,0,-1), (-1,2,0), and (2,-1,0). 3
 0, 1, 12, 456, 54216, 6932916, 1069256400, 170663949024, 29130191148240, 5115288488816760, 927446504770571520, 171486284915686699620, 32295496327107026335392, 6164943698859825359296740, 1190940852937573264531168944, 232287567721717805821704554232 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..400 FORMULA a(n) ~ c * 6^(3*n) / n, where c = 0.000020280187096503586851533... . - Vaclav Kotesovec, Oct 14 2016 MAPLE g():= combinat[permute]([0, -1, 2]): b:= proc(l) option remember; `if`(l=[1\$3], 1, add((p->       `if`(p[1]<0, 0, b(p)))(sort(l-x)), x=g()))     end: a:= n-> b([n\$3]): seq(a(n), n=0..20); MATHEMATICA g = Permutations[{0, -1, 2}]; b[l_] := b[l] = If[l == {1, 1, 1}, 1, Sum[Function[p, If[p[[1]] < 0, 0, b[p]]][Sort[l - x]], {x, g}]]; a[n_] := b[{n, n, n}]; Table[a[n], {n, 0, 20}] (* Jean-François Alcover, Mar 29 2017, translated from Maple *) CROSSREFS Cf. A048116. Sequence in context: A202799 A121348 A239365 * A226358 A225796 A112363 Adjacent sequences:  A277259 A277260 A277261 * A277263 A277264 A277265 KEYWORD nonn,walk AUTHOR Alois P. Heinz, Oct 07 2016 STATUS approved

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Last modified October 21 11:25 EDT 2019. Contains 328295 sequences. (Running on oeis4.)