A318590 Number of connected balanced simple signed graphs on n unlabeled nodes.

1, 1, 2, 5, 28, 177, 1982, 33997, 1020516, 54570672, 5347070228, 967135763525, 324200029119318, 202046821340636691, 234878262433630160622, 511060736355598412146405, 2088401066728281847415734793, 16079824271822965645002329491423, 233994776259866281916838227225733732

Offset: 0

Author

Andrew Howroyd, Sep 25 2018

Keywords

• nonn

Links

• Andrew Howroyd, Table of n, a(n) for n = 0..50
• Wikipedia, Signed graph

Crossrefs

Cf. A005142, A034892, A053465, A054919, A054921.

Formula

a(2*n+1) = A054921(2*n+1)/2, a(2*n) = (a(n) + A054919(n) + A054921(2*n) - A054921(n))/2.

Inverse Euler transform of A034892.