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A068932 Number of disconnected regular graphs with n nodes. 19
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

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

Row sums of A068933.

LINKS

Table of n, a(n) for n=0..24.

FORMULA

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

CROSSREFS

Cf. A005176, A005177, A068933.

Sequence in context: A034392 A181531 A034393 * A151533 A128100 A035579

Adjacent sequences:  A068929 A068930 A068931 * A068933 A068934 A068935

KEYWORD

hard,more,nonn

AUTHOR

David Wasserman, Mar 08 2002

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

STATUS

approved

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Last modified December 20 15:01 EST 2014. Contains 252266 sequences.