A068932 Number of disconnected regular graphs with n nodes.

0, 0, 1, 1, 2, 1, 3, 2, 5, 4, 9, 7, 23, 18, 74, 106, 619, 2076, 22526, 112834, 4799825, 31138965, 4207943011, 115979718015, 13482672647959

Offset: 0

Author

David Wasserman, Mar 08 2002

Keywords

• hard
• more
• nonn

Comments

A graph is called regular if every node has the same number of edges.

Row sums of A068933.

Crossrefs

Cf. A005176, A005177, A068933.

Formula

a(n) = A005176(n) - A005177(n).

Extensions

a(22) corrected and a(23) appended Sep 28 2009, a(24) appended Nov 24 2009, by Jason Kimberley.

a(0)=0 (due to the empty graph being vacuously connected) inserted by Jason Kimberley, Apr 11 2012