The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A052557 Expansion of e.g.f. (1-x)/(1-x-x^3). 0
 1, 0, 0, 6, 24, 120, 1440, 15120, 161280, 2177280, 32659200, 518918400, 9101030400, 174356582400, 3574309939200, 78460462080000, 1841205510144000, 45883678224384000, 1210048630382592000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 LINKS INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 499 FORMULA E.g.f.: (1-x)/(1 - x - x^3). a(n) = n*a(n-1) + n*(n-1)*(n-2)*a(n-3), where a(0)=1, a(1)=0, a(2)=0. a(n) = Sum(-1/31*(2+3*_alpha^2-11*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+_Z+_Z^3))*n!. a(n) = n!*A078012(n). - R. J. Mathar, Nov 27 2011 MAPLE spec := [S, {S=Sequence(Prod(Z, Z, Z, Sequence(Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20); MATHEMATICA With[{nn=20}, CoefficientList[Series[(1-x)/(1-x-x^3), {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Jun 20 2012 *) PROG (PARI) my(x='x+O('x^30)); Vec(serlaplace( (1-x)/(1-x-x^3) )) \\ G. C. Greubel, May 07 2019 (MAGMA) m:=30; R:=PowerSeriesRing(Rationals(), m); b:=Coefficients(R!( (1-x)/(1-x-x^3) )); [Factorial(n-1)*b[n]: n in [1..m]]; // G. C. Greubel, May 07 2019 (Sage) R = PowerSeriesRing(QQ, 'x') x = R.gen().O(30) T = (1-x)/(1-x-x^3) list(T.egf_to_ogf()) # G. C. Greubel, May 07 2019 (GAP) a:=[0, 0, 6];; for n in [4..30] do a[n]:=n*a[n-1]+n*(n-1)*(n-2)*a[n-3]; od; Concatenation([1], a); # G. C. Greubel, May 07 2019 CROSSREFS Sequence in context: A293049 A293123 A060249 * A188232 A274072 A224662 Adjacent sequences:  A052554 A052555 A052556 * A052558 A052559 A052560 KEYWORD easy,nonn AUTHOR encyclopedia(AT)pommard.inria.fr, Jan 25 2000 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 10 03:07 EDT 2022. Contains 356029 sequences. (Running on oeis4.)