A318590 Number of connected balanced 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

0,3

Links

Andrew Howroyd, Table of n, a(n) for n = 0..50

Wikipedia, Signed graph

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.

Crossrefs

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

Sequence in context: A047132 A364112 A264699 * A072371 A019043 A009635

Adjacent sequences: A318587 A318588 A318589 * A318591 A318592 A318593

Keyword

nonn

Author

Andrew Howroyd, Sep 25 2018

Status

approved