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A052829
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A simple grammar.
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1
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0, 1, 2, 4, 10, 25, 69, 197, 583, 1762, 5441, 17042, 54072, 173334, 560659, 1827306, 5995570, 19787135, 65643226, 218777532, 732181107, 2459576149, 8290442750, 28031056619, 95045477945, 323112137130, 1101073839413, 3760472582922, 12869488098939, 44127605854574
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OFFSET
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0,3
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LINKS
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FORMULA
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G.f.: (x/(1-x))*Product_{k>=1} (1+x^k)^a(k). - Vladeta Jovovic, Jul 22 2004
G.f. A(x) satisfies: A(x) = (x/(1 - x)) * exp(Sum_{k>=1} (-1)^(k+1) * A(x^k) / k). - Ilya Gutkovskiy, Jun 28 2021
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MAPLE
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spec := [S, {B=Sequence(Z, 1 <= card), C=PowerSet(S), S=Prod(C, B)}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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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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EXTENSIONS
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STATUS
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approved
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