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A052635 E.g.f. (1-3x)/(1-3x-x^2). 0
1, 0, 2, 18, 240, 3960, 78480, 1814400, 47940480, 1425029760, 47065536000, 1709915961600, 67769625369600, 2909762279424000, 134544087553075200, 6665534018567424000, 352236213903974400000, 19777072162153033728000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

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

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 581

FORMULA

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

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

Sum(1/13*(-3+11*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+3*_Z+_Z^2))*n!

MAPLE

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

CROSSREFS

Sequence in context: A260332 A254999 A024486 * A259270 A168562 A117514

Adjacent sequences:  A052632 A052633 A052634 * A052636 A052637 A052638

KEYWORD

easy,nonn

AUTHOR

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

STATUS

approved

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Last modified September 24 12:38 EDT 2021. Contains 347642 sequences. (Running on oeis4.)