OFFSET
0,6
COMMENTS
A bridge is an edge that, if removed without removing any incident vertices, disconnects the graph. Unlabeled graphs with no bridges are counted by A007146 (unlabeled graphs with spanning edge-connectivity >= 2).
LINKS
FORMULA
G.f.: (f(x)^2 + f(x^2))/2 where f(x) is the g.f. of A007145. - Andrew Howroyd, Aug 25 2019
MATHEMATICA
(f[x]^2 + f[x^2])/2 + O[x]^lg // CoefficientList[#, x]& (* Jean-François Alcover, Sep 23 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Aug 24 2019
EXTENSIONS
Terms a(6) and beyond from Andrew Howroyd, Aug 25 2019
STATUS
approved