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Search: id:A052570
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| 0, 1, 8, 96, 1536, 30720, 737280, 20643840, 660602880, 23781703680, 951268147200, 41855798476800, 2009078326886400, 104472072998092800, 5850436087893196800, 351026165273591808000, 22465674577509875712000
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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A simple regular expression in a labeled universe.
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 513
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FORMULA
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Recurrence: {a(1)=1, a(0)=0, (-4-4*n)*a(n)+a(n+1)}
4^(n-1)*n! for n >= 1.
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MAPLE
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spec := [S, {S=Prod(Z, Sequence(Union(Z, Z, Z, Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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A034177 is an essentially identical sequence. - Philippe DELEHAM, Sep 18 2008
Adjacent sequences: A052567 A052568 A052569 this_sequence A052571 A052572 A052573
Sequence in context: A060458 A098430 A034177 this_sequence A002168 A114425 A052127
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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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