A277478 E.g.f.: -cosh(x)*LambertW(-x).

0, 1, 2, 12, 76, 720, 8766, 131096, 2319416, 47361600, 1096018330, 28344108672, 810053677764, 25352185339520, 862335856149782, 31674845755622400, 1249527587684729584, 52687201308036059136, 2364751154207006978994, 112562199977955164819456

Offset

0,3

Links

G. C. Greubel, Table of n, a(n) for n = 0..385

Formula

a(n) = Sum_{k=1..n} (1 + (-1)^(n-k)) * binomial(n,k) * k^(k-1)/2.

a(n) ~ cosh(exp(-1)) * n^(n-1).

Mathematica

CoefficientList[Series[-Cosh[x]*LambertW[-x], {x, 0, 20}], x] * Range[0, 20]!
Table[Sum[(1 + (-1)^(n-k)) * Binomial[n, k] * k^(k-1)/2, {k, 1, n}], {n, 0, 20}]

Prog

(PARI) x='x+O('x^50); concat([0], Vec(serlaplace(-cosh(x)*lambertw(-x)))) \\ G. C. Greubel, Nov 07 2017

Crossrefs

Cf. A000169, A277464, A277473, A277476, A277477.

Sequence in context: A198474 A285489 A121680 * A372410 A372233 A081014

Adjacent sequences: A277475 A277476 A277477 * A277479 A277480 A277481

Keyword

nonn

Author

Vaclav Kotesovec, Oct 17 2016

Status

approved