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Search: id:A124504
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| A124504 |
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Number of partitions of an n-set without blocks of size 3. |
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+0
2
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| 1, 1, 2, 4, 11, 32, 113, 422, 1788, 8015, 39435, 204910, 1144377, 6722107, 41877722, 273328660, 1875326627, 13427171644, 100415636519, 780856389454, 6312398830812, 52891894374481, 459022366424253, 4117482357137214
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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a(n)=A124503(n,0).
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FORMULA
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E.g.f.: exp(exp(x)-1-x^3/6).
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EXAMPLE
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a(3)=4 because if the set is {1,2,3}, then we have 1|2|3, 1|23, 12|3 and 13|2.
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MAPLE
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G:=exp(exp(x)-1-x^3/6): Gser:=series(G, x=0, 30): seq(n!*coeff(Gser, x, n), n=0..26);
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CROSSREFS
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Cf. A124503.
Sequence in context: A156043 A148171 A113774 this_sequence A056324 A056325 A103293
Adjacent sequences: A124501 A124502 A124503 this_sequence A124505 A124506 A124507
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KEYWORD
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nonn
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AUTHOR
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Emeric Deutsch (deutsch(AT)duke.poly.edu), Nov 14 2006
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