1,5

Table of n, a(n) for n=1..9.

Gordon Royle, Small Graphs: Class 2 Graphs.

Eric Weisstein's World of Mathematics, Class 2 Graph

a(n) = A001349(n) - A099436(n). - Andrew Howroyd, Sep 03 2019

Cf. A001349 (number of connected graphs on n nodes).

Cf. A099437 (number of simple class-2 graphs on n nodes).

Cf. A099436 (number of connected class-1 graphs on n nodes).

Sequence in context: A127138 A064081 A211364 * A002178 A013558 A161000

Adjacent sequences: A099435 A099436 A099437 * A099439 A099440 A099441

nonn,more

Eric W. Weisstein, Oct 15 2004

approved