A320499 - OEIS

%I #17 Jan 28 2020 03:41:40

%S 1,1,0,1,3,14,62,572,7409,163284,5736443,342169618,33534945769,

%T 5442700283638,1484664946343496,664513607618098252,

%U 508538464299389501337,635542752091150346032474,1374528064543283977151585962,4842758246111267151697826493193

%N Number of connected self-dual signed graphs with n nodes.

%H Edward A. Bender and E. Rodney Canfield, <a href="https://doi.org/10.1016/0095-8956(83)90040-0">Enumeration of connected invariant graphs</a>, Journal of Combinatorial Theory, Series B 34.3 (1983): 268-278. See p. 273, fourth table.

%H Andrew Howroyd, <a href="/A320499/a320499.txt">PARI Program</a>

%F 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

%o (PARI) \\ See link for program.

%o A320499seq(20) \\ _Andrew Howroyd_, Jan 27 2020

%Y Cf. A004102 (signed graphs), A004104 (self-dual), A053465 (connected signed graphs).

%K nonn

%O 0,5

%A _N. J. A. Sloane_, Oct 26 2018

%E Dead sequence restored by _Andrew Howroyd_, Jan 26 2020

%E a(0)=1 prepended and terms a(13) and beyond from _Andrew Howroyd_, Jan 26 2020