A320491 Number of connected edge-self-dual nets with n nodes.

1, 2, 0, 4, 13, 98, 748, 9982, 205290, 6546960, 352371887, 29668304472, 4303531187466, 985391751078694, 391866509275972993, 248491878411568471280, 274544424465100159954078, 488310442484985365942048784, 1513516279388226593561422201905

Offset

0,2

Links

Table of n, a(n) for n=0..18.

Edward A. Bender and E. Rodney Canfield, Enumeration of connected invariant graphs, Journal of Combinatorial Theory, Series B 34.3 (1983): 268-278. See p. 275.

Andrew Howroyd, PARI Program

Formula

a(2*n-1) = b(2*n-1), a(2*n) = b(2*n) - (A320489(n) - a(n))/2 where b is the Inverse Euler transform of A004106.

Prog

(PARI) \\ See link for program.
A320491seq(20) \\ Andrew Howroyd, Jan 28 2020

Crossrefs

Cf. A004103 (nets), A004106 (edge-self-dual), A320489 (connected nets).

Sequence in context: A361269 A343472 A214199 * A295907 A317364 A265664

Adjacent sequences: A320488 A320489 A320490 * A320492 A320493 A320494

Keyword

nonn

Author

N. J. A. Sloane, Oct 25 2018

Extensions

Dead sequence restored, corrected and extended by Andrew Howroyd, Jan 28 2020

Status

approved