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Search: id:A130220
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| A130220 |
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Number of partitions of n-set in which number of blocks of size k is odd (or zero) for every k. |
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+0
3
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| 1, 1, 1, 5, 5, 27, 117, 331, 1213, 6579, 47193, 140527, 1213841, 4617927, 48210879, 243443739, 2392565149, 10377087115, 125434781845, 725455816883, 8086277450629, 59694530600595, 614469256831895, 4650128350629285
(list; graph; listen)
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OFFSET
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0,4
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FORMULA
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E.g.f.: Product_{k>0} (1+sinh(x^k/k!)).
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EXAMPLE
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a(4)=5 because we have abcd, a|bcd, acd|b, abd|c, and abc|d.
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MAPLE
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g:=product(1+sinh(x^k/factorial(k)), k=1..30): gser:=series(g, x=0, 28): seq(factorial(n)*coeff(gser, x, n), n=0..24); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Sep 01 2007
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CROSSREFS
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Cf. A055922, A102759, A111723, A111724.
Sequence in context: A074872 A038247 A093643 this_sequence A081847 A020551 A117858
Adjacent sequences: A130217 A130218 A130219 this_sequence A130221 A130222 A130223
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KEYWORD
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easy,nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)Eunet.yu), Aug 04 2007, Aug 05 2007
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Sep 01 2007
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