A052867 E.g.f.: log(-(-1+x)^2/(-1+2*x)).

0, 0, 2, 12, 84, 720, 7440, 90720, 1280160, 20563200, 370863360, 7424524800, 163419379200, 3923023104000, 102011054745600, 2856483889459200, 85697132032512000, 2742350070620160000, 93240613775941632000

Offset

0,3

Comments

Previous name was: A simple grammar.

Links

Table of n, a(n) for n=0..18.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 838

Formula

D-finite with Recurrence: {a(1)=0, a(2)=2, (2*n^2+2*n)*a(n)-3*(n+1)*a(n+1)+a(n+2)}.

a(n) = -2*GAMMA(n+1)+2^(n+1)*GAMMA(n+1).

a(n) = 2*A052589(n-1). - R. J. Mathar, Jun 03 2022

Maple

spec := [S, {B=Sequence(Z, 1 <= card), C=Prod(B, B), S= Cycle(C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);

Mathematica

Range[0, 19]! CoefficientList[Series[Log[-(-1 + x)^2/(-1 + 2 x)], {x, 0, 19}], x] (* Vincenzo Librandi, Jul 09 2015 *)

Crossrefs

Sequence in context: A362245 A362237 A052887 * A226238 A179495 A348765

Adjacent sequences: A052864 A052865 A052866 * A052868 A052869 A052870

Keyword

easy,nonn

Author

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

Status

approved