|
| |
|
|
A052745
|
|
A simple grammar.
|
|
0
| |
|
|
0, 0, 0, 6, 24, 110, 600, 3836, 28224, 235224, 2191680, 22584672, 255087360, 3134139840, 41620400640, 594082771200, 9070900715520, 147531542054400, 2546434166169600, 46489412442009600, 895079522340864000
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,4
|
|
|
LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 701
|
|
|
FORMULA
| E.g.f.: ln(-1/(-1+x))^2*x
Recurrence: {a(1)=0, a(2)=0, a(3)=6, (-n+n^4+n^3-3*n^2+2)*a(n)+(-2*n^3-3*n^2+2*n)*a(n+1)+(n^2+n)*a(n+2)}
a(n) = (-1)^(n+1)*2*n*Stirling1(n-1, 2). - Vladeta Jovovic (vladeta(AT)eunet.rs), Nov 08 2003
|
|
|
MAPLE
| spec := [S, {B=Cycle(Z), S=Prod(Z, B, B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
|
|
|
PROG
| (Maxima) makelist((-1)^(n+1)*2*n*stirling1(n-1, 2), n, 0, 20); [Bruno Berselli, May 25 2011]
|
|
|
CROSSREFS
| Sequence in context: A075484 A122739 A038380 * A187668 A109583 A100934
Adjacent sequences: A052742 A052743 A052744 * A052746 A052747 A052748
|
|
|
KEYWORD
| easy,nonn
|
|
|
AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
|
| |
|
|
