A129435 Number of isomorphism classes of 7-regular multigraphs of order 2n, loops allowed.

4, 101, 12782, 8584767, 20104116089, 122644465172798, 1658339657066189475, 44564623565972592394826, 2193250056291167380214634054, 185389574171283940222059091478222

Offset: 1

Author

Brendan McKay, Apr 15 2007

Keywords

• nonn
• more

Comments

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

Links

• R. C. Read, The enumeration of locally restricted graphs (I), J. London Math. Soc. 34 (1959) 417-436.

Crossrefs

Column k=7 of A167625.

Cf. A129434, A129424, A129427, A129429, A129431, A129433, A129437.

Formula

a(n) = N\{S_{2n}[S_7] * S_{7n}[S_2]\}.

Euler transform of A129434. - Andrew Howroyd, Mar 15 2020

Extensions

Using equation (5.8) of Read 1959, McKay's terms were verified by, and new term a(6) was computed by Jason Kimberley, Nov 09 2009

a(7)-a(10) from Andrew Howroyd, Mar 21 2020