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A052872
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A simple grammar.
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0
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1, 1, 3, 9, 32, 117, 460, 1850, 7680, 32467, 139631, 608280, 2679881, 11916492, 53417407, 241118245, 1095030281, 4999847240, 22938576846, 105690791104, 488860041249
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 843
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MAPLE
| spec := [S, {C=Sequence(B, 1 <= card), S=Set(C), B=Prod(Z, S)}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A194353 A148985 A148986 * A122452 A192206 A091841
Adjacent sequences: A052869 A052870 A052871 * A052873 A052874 A052875
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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