A052576 E.g.f. (1+x^2-2x^3)/(1-2x).

1, 2, 10, 48, 384, 3840, 46080, 645120, 10321920, 185794560, 3715891200, 81749606400, 1961990553600, 51011754393600, 1428329123020800, 42849873690624000, 1371195958099968000, 46620662575398912000

Offset

0,2

Links

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

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 519

Formula

E.g.f.: (-x^2+2*x^3-1)/(-1+2*x)

Recurrence: {a(0)=1, a(1)=2, (-2*n-2)*a(n)+a(n+1)=0, a(2)=10, a(3)=48}

2^n*n!, n>2.

Maple

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

Crossrefs

Essentially the same as A000165 (which is the main entry).

Sequence in context: A037256 A270664 A330543 * A279852 A219662 A355153

Adjacent sequences: A052573 A052574 A052575 * A052577 A052578 A052579

Keyword

easy,nonn

Author

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

Status

approved