A174636 Integral_{x=0..infinity} (x + x^2 + x^3)^n exp(-x).

1, 9, 1046, 519918, 681617304, 1853340127320, 9049964145536880, 72083636411763075120, 874164613833481641471360, 15325066482283901592487889280, 372998446683217113984893861356800

Offset

0,2

Links

Table of n, a(n) for n=0..10.

Mathematica

Trinomial[n_, k_] := If[k == 0, 1, Coefficient[(1 + x + x^2)^n, x^k]]; a[n_] := Sum[Trinomial[n, k](n + k)!, {k, 0, 2n}]; Table[a[n], {n, 0, 20}]

Crossrefs

Sequence in context: A172944 A277829 A286396 * A374143 A054344 A372652

Adjacent sequences: A174633 A174634 A174635 * A174637 A174638 A174639

Keyword

nonn

Author

Emanuele Munarini, Jan 25 2011

Status

approved