A052745 A simple grammar.

0, 0, 0, 6, 24, 110, 600, 3836, 28224, 235224, 2191680, 22584672, 255087360, 3134139840, 41620400640, 594082771200, 9070900715520, 147531542054400, 2546434166169600, 46489412442009600, 895079522340864000, 18125736166340812800, 385129713617510400000

Offset

0,4

Links

Table of n, a(n) for n=0..22.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 701

Formula

E.g.f.: log(-1/(-1+x))^2*x.

Recurrence: a(1)=0, a(2)=0, a(3)=6, (-n+n^4+n^3-3*n^2+2)*a(n)+(-2*n^3-3*n^2+2*n)*a(n+1)+(n^2+n)*a(n+2)=0.

a(n) = (-1)^(n+1)*2*n*Stirling1(n-1, 2). - Vladeta Jovovic, Nov 08 2003

Maple

spec := [S, {B=Cycle(Z), S=Prod(Z, B, B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);

Mathematica

Range[0, 30]! CoefficientList[Series[Log[-1/(-1 + x)]^2 x, {x, 0, 30}], x] (* Vincenzo Librandi, Jul 08 2015 *)

Prog

(Maxima) makelist((-1)^(n+1)*2*n*stirling1(n-1, 2), n, 0, 20); /* Bruno Berselli, May 25 2011 */
(Magma) [0] cat [(-1)^(n+1)*2*n*StirlingFirst(n-1, 2): n in [1..30]]; // Vincenzo Librandi, Jul 08 2015

Crossrefs

Sequence in context: A075484 A122739 A038380 * A187668 A273813 A293257

Adjacent sequences: A052742 A052743 A052744 * A052746 A052747 A052748

Keyword

easy,nonn

Author

encyclopedia(AT)pommard.inria.fr, Jan 25 2000

Status

approved