|
| |
| |
|
|
|
3, 3, 6, 18, 72, 360, 2160, 15120, 120960, 1088640, 10886400, 119750400, 1437004800, 18681062400, 261534873600, 3923023104000, 62768369664000, 1067062284288000, 19207121117184000, 364935301226496000, 7298706024529920000, 153272826515128320000
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,1
|
|
|
COMMENTS
| a(n) is the size of the centralizer of a 3-cycle in the symmetric group S_(n+3). - Ahmed Fares (ahmedfares(AT)my-deja.com), May 12 2001
3 times factorial numbers. [From Omar E. Pol (info(AT)polprimos.com), Jan 17 2009]
|
|
|
LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 0..200
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 502
|
|
|
FORMULA
| E.g.f.: -3/(-1+x)
Recurrence: {(-1-n)*a(n)+a(n+1), a(0)=3}
For n>0: a(n) = SUM(A083746(k): 1<=k<=n+1). - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Apr 14 2007
|
|
|
MAPLE
| spec := [S, {S=Union(Sequence(Z), Sequence(Z), Sequence(Z))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
a:=n->sum(n!, k=1..n):seq(a(n)-sum(n!, k=4..n), n=0...19); # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 22 2008]
|
|
|
MATHEMATICA
| Table[3*n!, {n, 0, 50}] (* From Vladimir Joseph Stephan Orlovsky, Jun 12 2011 *)
|
|
|
PROG
| (MAGMA) [3*Factorial(n): n in [0..20]]; // Vincenzo Librandi, Jun 13 2011
(PARI) a(n)=3*n! \\ Charles R Greathouse IV, Nov 20 2011
|
|
|
CROSSREFS
| Cf. A129380, A000142.
Sequence in context: A132818 A134068 A025256 * A147836 A019235 A103895
Adjacent sequences: A052557 A052558 A052559 * A052561 A052562 A052563
|
|
|
KEYWORD
| easy,nonn
|
|
|
AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
|
| |
|
|
