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Search: id:A052673
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| A052673 |
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A simple regular expression in a labeled universe. |
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+0
3
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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; listen)
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OFFSET
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0,2
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 621
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FORMULA
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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}
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
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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
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Sequence in context: A006026 A158826 A107264 this_sequence A042971 A024038 A007199
Adjacent sequences: A052670 A052671 A052672 this_sequence A052674 A052675 A052676
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KEYWORD
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easy,nonn
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AUTHOR
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encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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