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0, 3, 12, 54, 288, 1800, 12960, 105840, 967680, 9797760, 108864000, 1317254400, 17244057600, 242853811200, 3661488230400, 58845346560000, 1004293914624000, 18140058832896000, 345728180109312000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 621
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FORMULA
| E.g.f.: 3*x/(-1+x)^2
Recurrence: {a(0)=0, a(1)=3, (-n^2-2*n-1)*a(n)+a(n+1)*n =0}
3*n*n!
a(n) = A122972(n+2) - A122972(n) for n > 0. - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Sep 21 2006
For n>0: a(n) = A083746(n+2). - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Apr 14 2007
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MAPLE
| spec := [S, {S=Prod(Sequence(Z), Sequence(Z), Union(Z, Z, Z))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A177133 A186241 A193115 * A180589 A042971 A024038
Adjacent sequences: A052670 A052671 A052672 * A052674 A052675 A052676
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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