A052876 Expansion of e.g.f. (exp(x)-1)^2/(-2+exp(x))^2.

0, 0, 2, 18, 158, 1530, 16622, 201978, 2724878, 40492890, 657944942, 11611834938, 221291822798, 4530383962650, 99179581033262, 2312402554523898, 57211901491595918, 1497211181084718810

Offset

0,3

Comments

Previous name was: A simple grammar.

Links

Table of n, a(n) for n=0..17.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 847

Formula

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

From Mario Catalani (mario.catalani(AT)unito.it), Dec 22 2003: (Start)

a(n) = A069321(n) - A000670(n).

a(n) = 2*A091106(n)+2. (End)

Maple

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

Mathematica

With[{nn=20}, CoefficientList[Series[((Exp[x]-1)^2/(Exp[x]-2)^2), {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Jul 19 2018 *)

Crossrefs

Cf. A000670, A069321, A091106.

Sequence in context: A386514 A366953 A052838 * A121933 A108550 A322282

Adjacent sequences: A052873 A052874 A052875 * A052877 A052878 A052879

Keyword

easy,nonn

Author

INRIA Encyclopedia of Combinatorial Structures, Jan 25 2000

Extensions

Name changed by Wesley Ivan Hurt, Jun 26 2022

Status

approved