A109780 - OEIS

A109780

a(n) = n! * Sum_{k=1..n} H(k)*(n-k)!, where H(k) = Sum_{j=1..k} 1/j.

1, 5, 32, 310, 4924, 126648, 4869192, 258608880, 17973530784, 1576566817920, 170028329630400, 22092970356011520, 3402396234446595840, 612619882946124157440, 127484451712085785228800, 30358069092698014483200000, 8201548600725828770272972800

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OFFSET

1,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..200

FORMULA

E.g.f.: hypergeom([1, 1], [], x)*log(1-x)/(x-1). - Vladeta Jovovic, Aug 16 2005

MATHEMATICA

f[n_] := n! * Sum[(n-k)! * Sum[1/j, {j, 1, k}], {k, 1, n}]; Table[f[n], {n, 1, 30}] (* Ryan Propper, Aug 18 2005 *)

PROG

(PARI) a(n) = n!*sum(k=1, n, sum(j=1, k, 1/j)*(n-k)!); \\ Michel Marcus, Nov 20 2018

CROSSREFS

Cf. A109779.

Sequence in context: A294957 A363397 A023882 * A093448 A094653 A135250

Adjacent sequences: A109777 A109778 A109779 * A109781 A109782 A109783

KEYWORD

nonn

AUTHOR

Leroy Quet, Aug 13 2005

EXTENSIONS

More terms from Ryan Propper, Aug 18 2005

STATUS

approved