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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A052700 Expansion of e.g.f. x*(1-x)/(1-3*x). 1
 0, 1, 4, 36, 432, 6480, 116640, 2449440, 58786560, 1587237120, 47617113600, 1571364748800, 56569130956800, 2206196107315200, 92660236507238400, 4169710642825728000, 200146110855634944000, 10207451653637382144000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS G. C. Greubel, Table of n, a(n) for n = 0..375 INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 650 FORMULA E.g.f.: x*(1-x)/(1-3*x) D-finite recurrence: a(1)=1, a(0)=0, a(2)=4, a(n) = 3*n*a(n-1). a(n) = 2*3^(n-2)*n! = 2*A153647(n-2), n>1. MAPLE spec := [S, {S=Prod(Z, Sequence(Prod(Sequence(Z), Union(Z, Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20); MATHEMATICA Table[2*3^(n-2)*n! -2*Boole[n==0]/9 + Boole[n==1]/3, {n, 0, 30}] (* G. C. Greubel, May 31 2022 *) With[{nn=30}, CoefficientList[Series[x (1-x)/(1-3x), {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Oct 19 2022 *) PROG (SageMath) [0, 1]+[2*3^(n-2)*factorial(n) for n in (2..30)] # G. C. Greubel, May 31 2022 CROSSREFS Cf. A153647. Sequence in context: A317147 A132864 A294050 * A167540 A136224 A321963 Adjacent sequences: A052697 A052698 A052699 * A052701 A052702 A052703 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 September 26 15:44 EDT 2023. Contains 365660 sequences. (Running on oeis4.)