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A052584 E.g.f. (2-4x+x^2)/((1-x)(1-2x)). 2
2, 2, 6, 30, 216, 2040, 23760, 327600, 5201280, 93260160, 1861574400, 40914720000, 981474278400, 25512104217600, 714251739801600, 21426244519680000, 685618901839872000, 23310686975127552000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

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

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 529

FORMULA

E.g.f.: (2-4*x+x^2)/(-1+2*x)/(-1+x)

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

(1+2^(n-1))*n!, n>0, see A000051.

Contribution from Peter Luschny, Apr 20 2009: (Start)

A weighted binomial sum of the Bernoulli numbers A027641/A027642 with A027641(1)=1 (which amounts to the definition B_{n} = B_{n}(1)).

a(n) = Sum_{k=0..n-1} n!*C(n-1,k)*B_{n-k-1}*2^(k+1)/(k+1). (See also A000051.) (End)

MAPLE

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

a := proc(n) if n = 0 then 2 else add(n!*binomial(n-1, k)*bernoulli(n-k-1, 1)*2^(k+ 1)/(k+1), k=0..n-1) fi end: [From Peter Luschny, Apr 20 2009]

CROSSREFS

Sequence in context: A184312 A097801 A164347 * A094303 A117394 A267073

Adjacent sequences:  A052581 A052582 A052583 * A052585 A052586 A052587

KEYWORD

easy,nonn

AUTHOR

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

STATUS

approved

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Last modified June 23 21:29 EDT 2017. Contains 288675 sequences.