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A320499
Number of connected self-dual signed graphs with n nodes.
2
1, 1, 0, 1, 3, 14, 62, 572, 7409, 163284, 5736443, 342169618, 33534945769, 5442700283638, 1484664946343496, 664513607618098252, 508538464299389501337, 635542752091150346032474, 1374528064543283977151585962, 4842758246111267151697826493193
OFFSET
0,5
LINKS
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. 273, fourth table.
Andrew Howroyd, PARI Program
FORMULA
a(2*n-1) = b(2*n-1), a(2*n) = b(2*n) - (A053465(n) - a(n))/2 where b is the Inverse Euler transform of A004104. - Andrew Howroyd, Jan 27 2020
PROG
(PARI) \\ See link for program.
A320499seq(20) \\ Andrew Howroyd, Jan 27 2020
CROSSREFS
Cf. A004102 (signed graphs), A004104 (self-dual), A053465 (connected signed graphs).
Sequence in context: A100295 A376894 A291025 * A091701 A242637 A151237
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Oct 26 2018
EXTENSIONS
Dead sequence restored by Andrew Howroyd, Jan 26 2020
a(0)=1 prepended and terms a(13) and beyond from Andrew Howroyd, Jan 26 2020
STATUS
approved