A324217 Number of connected 2n-regular loopless multigraphs on seven unlabeled nodes.

0, 1, 50, 933, 12465, 119906, 864705, 4930446, 23280925, 94308983, 336704397, 1081565510, 3176476119, 8638660038, 21978039571, 52745266132, 120228555981, 261785061087, 547126506745, 1102086250237, 2147107495684

Offset

0,3

Comments

There are no (2n+1)-regular graphs satisfying the condition above.

Multigraphs are loopless.

Initial terms computed with 'nauty and Traces' (see the link).

Links

Table of n, a(n) for n=0..20.

Brendan McKay and Adolfo Piperno, nauty and Traces

Prog

(nauty) for ((n=0; n<30; n=n+2)); do geng -c -d1 7 -q | multig -r${n} -u; done

Crossrefs

Row n=7 of A328682.

Cf. A324218.

Sequence in context: A329713 A101929 A006360 * A224059 A224045 A224276

Adjacent sequences: A324214 A324215 A324216 * A324218 A324219 A324220

Keyword

nonn,more,hard

Author

Natan Arie Consigli, Apr 30 2019

Extensions

a(10)-a(20) from Andrew Howroyd, Mar 17 2020

Status

approved