login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual Appeal: Today, Nov 11 2014, is the 4th anniversary of the launch of the new OEIS web site. 70,000 sequences have been added in these four years, all edited by volunteers. Please make a donation (tax deductible in the US) to help keep the OEIS running.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A097762 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. 1
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; refs; listen; history; text; internal format)
OFFSET

1,6

LINKS

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

FORMULA

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

EXAMPLE

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.

MAPLE

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

CROSSREFS

Cf. A000296, A097763.

Sequence in context: A146211 A195806 A081588 * A083469 A224160 A224411

Adjacent sequences:  A097759 A097760 A097761 * A097763 A097764 A097765

KEYWORD

easy,nonn

AUTHOR

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

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .

Last modified November 27 21:59 EST 2014. Contains 250286 sequences.