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A097763
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Number of different partitions of the set {1, 2, ..., n} into an even number of blocks such that each block contains at least 2 elements.
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2
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0, 0, 0, 3, 10, 25, 56, 224, 1506, 9951, 57992, 315425, 1761552, 11022180, 78474748, 603715831, 4771273414, 38070877273, 309146434240, 2598546954268, 22887194502518, 211388690471531, 2031261113410564, 20121026325645745
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OFFSET
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1,4
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COMMENTS
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A097762(n)+A097763(n) = A000296(n).
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LINKS
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Table of n, a(n) for n=1..24.
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FORMULA
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Exponential generating function: cosh(exp(x)-x-1).
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EXAMPLE
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a(6)=25 since we can partition a set of six elements into two non-singleton blocks, either of sizes four and two (15 ways) or three and three (10 ways); a(6)=15+10=25.
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MAPLE
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seq(coeff(series(cosh(exp(x)-x-1), x=0, 25), x^i)*i!, i=1..24);
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CROSSREFS
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Cf. A000296, A097762.
Sequence in context: A047667 A192963 A000247 * A034506 A067988 A005674
Adjacent sequences: A097760 A097761 A097762 * A097764 A097765 A097766
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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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STATUS
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approved
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