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A052554 Expansion of e.g.f.: (1-x)/(1 - x - x^2). 2
1, 0, 2, 6, 48, 360, 3600, 40320, 524160, 7620480, 123379200, 2195424000, 42631142400, 896690995200, 20312541849600, 492993236736000, 12762901831680000, 351063491530752000, 10224590808047616000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Number of ways to use the elements of {1,..,n} once each to form a sequence of lists, each having length at least 2. - Bob Proctor, Apr 19 2005

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..415

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 493

Robert A. Proctor, Let's Expand Rota's Twelvefold Way For Counting Partitions!, arXiv:math/0606404 [math.CO], 2006-2007.

Index entries for related partition-counting sequences

FORMULA

a(n) = n*a(n-1) + n*(n-1)*a(n-2), with a(0)=1, a(1)=0.

a(n) = Sum(1/5*(-1+3*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+_Z+_Z^2))*n!.

a(n) = n!*Fibonacci(n-1) for n >= 1. - Bob Proctor, Apr 19 2005

MAPLE

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

MATHEMATICA

With[{m=20}, CoefficientList[Series[(1-x)/(1-x-x^2), {x, 0, m}], x]* Range[0, m]!] (* G. C. Greubel, May 07 2019 *)

PROG

(PARI) my(x='x+O('x^20)); Vec(serlaplace( (1-x)/(1-x-x^2) )) \\ G. C. Greubel, May 07 2019

(MAGMA) [1] cat [Fibonacci(n-1)*Factorial(n): n in [1..20]] // G. C. Greubel, May 07 2019

(Sage) [1]+[fibonacci(n-1)*factorial(n) for n in (1..20)] # G. C. Greubel, May 07 2019

(GAP) a:=[0, 2];; for n in [3..20] do a[n]:=n*a[n-1]+n*(n-1)*a[n-2]; od; Concatenation([1], a); # G. C. Greubel, May 07 2019

CROSSREFS

Sequence in context: A239836 A052593 A052586 * A228159 A249786 A292934

Adjacent sequences:  A052551 A052552 A052553 * A052555 A052556 A052557

KEYWORD

easy,nonn

AUTHOR

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

STATUS

approved

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Last modified January 25 03:49 EST 2020. Contains 331241 sequences. (Running on oeis4.)