A129418 - OEIS

A129418

Number of isomorphism classes of 4-regular loopless multigraphs of order n.

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