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A097763 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. 2
0, 0, 0, 3, 10, 25, 56, 224, 1506, 9951, 57992, 315425, 1761552, 11022180, 78474748, 603715831, 4771273414, 38070877273, 309146434240, 2598546954268, 22887194502518, 211388690471531, 2031261113410564, 20121026325645745 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

A097762(n)+A097763(n) = A000296(n).

LINKS

Table of n, a(n) for n=1..24.

FORMULA

Exponential generating function: cosh(exp(x)-x-1).

EXAMPLE

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.

MAPLE

seq(coeff(series(cosh(exp(x)-x-1), x=0, 25), x^i)*i!, i=1..24);

CROSSREFS

Cf. A000296, A097762.

Sequence in context: A047667 A192963 A000247 * A034506 A067988 A005674

Adjacent sequences:  A097760 A097761 A097762 * A097764 A097765 A097766

KEYWORD

easy,nonn

AUTHOR

Isabel C. Lugo (izzycat(AT)gmail.com), Aug 23 2004

STATUS

approved

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Last modified December 22 12:40 EST 2014. Contains 252356 sequences.