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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A218696 Number of components over all graphs on n labeled nodes with unicyclic components (graphs counted by A137916). 1
1, 15, 222, 3680, 69345, 1477182, 35234220, 932070708, 27109785510, 860394764515, 29600058300780, 1097511032533500, 43637308561557074, 1852311640075120980, 83612841417061582320, 3999611090385007608840, 202111299843794061251580, 10758947714752854861908379 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,2

LINKS

Alois P. Heinz, Table of n, a(n) for n = 3..150

FORMULA

a(n) = Sum_{m=1..floor(n/3)} A106239(n,m)*m.

MATHEMATICA

nn=22; t=Sum[n^(n-1)x^n/n!, {n, 1, nn}]; Drop[Range[0, nn]!CoefficientList[ Series[D[Exp[y(Log[1/(1-t)]/2-t/2-t^2/4)], y]/.y->1, {x, 0, nn}], x], 3]

CROSSREFS

Cf. A057500.

Sequence in context: A279530 A057500 A137916 * A297669 A171320 A078364

Adjacent sequences:  A218693 A218694 A218695 * A218697 A218698 A218699

KEYWORD

nonn

AUTHOR

Geoffrey Critzer, Nov 04 2012

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 18 04:44 EST 2019. Contains 329248 sequences. (Running on oeis4.)