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A129418 Number of isomorphism classes of 4-regular loopless multigraphs of order n. 8
1, 0, 1, 1, 4, 7, 24, 60, 240, 930, 4701, 26637, 178569, 1339529, 11187064, 101871881, 1002594996, 10574095327, 118850827173, 1417140114336, 17860018997346, 237160827107408, 3309078044759285, 48396906463199522, 740331404753448181, 11821525310570525197 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

Initial terms computed using software at http://users.cecs.anu.edu.au/~bdm/nauty/

Also number of carbon allotropes satisfying the octet rule, excluding stereoisomers. - Natan Arie Consigli, Jun 06 2017

LINKS

Table of n, a(n) for n=0..25.

FORMULA

Euler transform of A129417. - Andrew Howroyd, Mar 14 2020

PROG

(nauty/bash) geng -d1 ${n} -q | multig -r4 -u # Natan Arie Consigli, Jun 06 2017

CROSSREFS

Column k=4 of A333330.

Cf. A129417, A129429, A129416, A129420, A129422, A129424, A129426.

Sequence in context: A203230 A143608 A079441 * A073218 A276288 A219700

Adjacent sequences:  A129415 A129416 A129417 * A129419 A129420 A129421

KEYWORD

nonn

AUTHOR

Brendan McKay, Apr 15 2007

EXTENSIONS

a(0)-a(1) by Natan Arie Consigli, Jun 06 2017

a(18)-a(25) from Andrew Howroyd, Mar 17 2020

STATUS

approved

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Last modified June 7 05:20 EDT 2020. Contains 334837 sequences. (Running on oeis4.)