%I #15 Jun 02 2025 17:23:48

%S 0,0,1,20,204,1689,13303,90614,543116,2842431,13218770,55233883,

%T 210199115,736166006,2395665563,7301022565,20981692199,57188601747,

%U 148588072319,369611918382,883579452509,2036672785494,4539872512172,9811474182969,20605911433906,42141179374995

%N Number of connected n-regular loopless multigraphs on eight unlabeled nodes.

%C Multigraphs are loopless.

%C Initial terms computed using 'Nauty and Traces' (see the link).

%H Andrew Howroyd, <a href="/A325474/b325474.txt">Table of n, a(n) for n = 0..30</a>

%H Brendan McKay and Adolfo Piperno, <a href="http://pallini.di.uniroma1.it">Nauty and Traces</a>

%o (nauty) for ((n=0;n<11;n++)); do geng -c -d1 8 -q | multig -r${n} -u; done

%Y Row n=8 of A328682.

%Y Cf. A324217, A324218.

%K nonn,hard

%O 0,4

%A _Natan Arie Consigli_, Aug 09 2019

%E Terms a(13) and beyond from _Andrew Howroyd_, Mar 17 2020