A052619 E.g.f. 3x^3/(1-x).

0, 0, 0, 18, 72, 360, 2160, 15120, 120960, 1088640, 10886400, 119750400, 1437004800, 18681062400, 261534873600, 3923023104000, 62768369664000, 1067062284288000, 19207121117184000, 364935301226496000

Offset

0,4

Links

Table of n, a(n) for n=0..19.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 564

Formula

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

Recurrence: {a(1)=0, a(0)=0, a(2)=0, (-1-n)*a(n)+a(n+1)=0, a(3)=18}

3*n!, n>2.

E.g.f. G(0)*3*x^3 where G(k)= 1 + x/(1 - x/( x + 1/G(k+1))); (continued fraction, 3rd kind, 3-step). - Sergei N. Gladkovskii, Jul 28 2012

Maple

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

Crossrefs

Sequence in context: A069058 A262000 A007276 * A110753 A154670 A041626

Adjacent sequences: A052616 A052617 A052618 * A052620 A052621 A052622

Keyword

easy,nonn

Author

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

Status

approved