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A052831
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A simple grammar.
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0
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0, 1, 2, 4, 11, 29, 91, 286, 955, 3235, 11240, 39559, 141217, 509059, 1852248, 6790372, 25062536, 93043286, 347223013, 1301777476, 4900835727, 18519492431, 70220471264, 267080436295, 1018708832722, 3895714521787, 14933608764343, 57372586025039, 220869710184189
(list;
graph;
refs;
listen;
history;
text;
internal format)
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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. satisfies A(x) = Sum_{j>=1} (phi(j)/j) * log( 1/(1-B(x^j)) ), where B(x) = x * exp( Sum_{j>=1} (-1)^(j+1) * S(x^j) / j ). - Sean A. Irvine, Dec 02 2021
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MAPLE
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spec := [S, {B=Prod(C, Z), C=PowerSet(S), S=Cycle(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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