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A052602 E.g.f. x^2*(1-x)/(1-x-x^2). 0
0, 0, 2, 0, 24, 120, 1440, 15120, 201600, 2903040, 47174400, 838252800, 16286054400, 342486144000, 7758867916800, 188305108992000, 4875010043904000, 134094160392192000, 3905447960494080000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

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

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 547

FORMULA

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

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

Sum(1/5*(-4+7*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+_Z+_Z^2))*n!

MAPLE

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

MATHEMATICA

With[{nn=30}, CoefficientList[Series[(x^2*(1-x))/(1-x-x^2), {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Dec 21 2011 *)

CROSSREFS

Sequence in context: A130915 A127067 A052607 * A012588 A012290 A012591

Adjacent sequences:  A052599 A052600 A052601 * A052603 A052604 A052605

KEYWORD

easy,nonn

AUTHOR

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

STATUS

approved

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Last modified September 22 21:07 EDT 2020. Contains 337291 sequences. (Running on oeis4.)