%I #20 Mar 17 2020 17:59:42

%S 1,0,1,1,4,7,24,60,240,930,4701,26637,178569,1339529,11187064,

%T 101871881,1002594996,10574095327,118850827173,1417140114336,

%U 17860018997346,237160827107408,3309078044759285,48396906463199522,740331404753448181,11821525310570525197

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

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

%C Also number of carbon allotropes satisfying the octet rule, excluding stereoisomers. - _Natan Arie Consigli_, Jun 06 2017

%F Euler transform of A129417. - _Andrew Howroyd_, Mar 14 2020

%o (nauty/bash) geng -d1 ${n} -q | multig -r4 -u # _Natan Arie Consigli_, Jun 06 2017

%Y Column k=4 of A333330.

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

%K nonn

%O 0,5

%A _Brendan McKay_, Apr 15 2007

%E a(0)-a(1) by _Natan Arie Consigli_, Jun 06 2017

%E a(18)-a(25) from _Andrew Howroyd_, Mar 17 2020