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Search: id:A097762
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| A097762 |
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Number of different partitions of the set {1, 2, ..., n} into an odd number of blocks such that each block contains at least 2 elements. |
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+0
2
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| 0, 1, 1, 1, 1, 16, 106, 491, 1919, 7771, 40261, 264892, 1871728, 12988977, 88413417, 612354549, 4492798353, 35529920764, 299329573882, 2625719242667, 23612697535919, 216981233646783, 2047084700918445, 19952633715109592
(list; graph; listen)
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OFFSET
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1,6
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FORMULA
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Exponential generating function: sinh(exp(x)-x-1).
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EXAMPLE
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a(6)=16 since we can partition a set of six labeled elements into one non-singleton block in 1 way and into three non-singleton blocks (each necessarily of size 2) in 15 ways; thus a(6)=1+15=16.
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MAPLE
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seq(coeff(series(sinh(exp(x)-x-1), x=0, 25), x^i)*i!, i=1..24);
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CROSSREFS
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Cf. A000296, A097763.
Sequence in context: A010079 A022708 A081588 this_sequence A083469 A056001 A053526
Adjacent sequences: A097759 A097760 A097761 this_sequence A097763 A097764 A097765
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KEYWORD
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easy,nonn
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AUTHOR
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Isabel C. Lugo (izzycat(AT)gmail.com), Aug 23 2004
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