A320994 Number of connected point-self-dual nets with 2n nodes.

1, 2, 37, 3264, 1798306, 7066174625, 208496688495494, 47481277563116098111, 85161165189313899034899294, 1221965295353715648352925546245057, 142024241427456183309163988600775633635361, 135056692113925953789612785828652550808044930178235

Offset

0,2

Links

Andrew Howroyd, Table of n, a(n) for n = 0..40

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. 274.

Andrew Howroyd, PARI Program

Formula

a(2*n-1) = b(2*n-1) - A320489(2*n-1)/2, a(2*n) = b(2*n) - (A320489(2*n)-a(n))/2 where b is the Inverse Euler transform of A004105. - Andrew Howroyd, Jan 27 2020

Prog

(PARI) \\ See link for program.
A320994seq(15) \\ Andrew Howroyd, Jan 27 2020

Crossrefs

Cf. A004103 (nets), A004105 (point-self-dual on 2n nodes), A320489 (connected nets).

Sequence in context: A234971 A139108 A165697 * A083189 A145798 A110762

Adjacent sequences: A320991 A320992 A320993 * A320995 A320996 A320997

Keyword

nonn

Author

N. J. A. Sloane, Oct 26 2018

Extensions

a(0)=1 prepended and terms a(7) and beyond from Andrew Howroyd, Jan 26 2020

Status

approved