A185144 Number of not necessarily connected 4-regular simple graphs on n vertices with girth exactly 4.

0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 2, 2, 12, 31, 220, 1606, 16829, 193900, 2452820, 32670331, 456028487, 6636066126, 100135577863, 1582718910743

Offset

0,11

Links

Table of n, a(n) for n=0..23.

Jason Kimberley, Index of sequences counting not necessarily connected k-regular simple graphs with girth exactly g

Formula

a(n) = A184944(n) + A185044(n) = A185140(n,4).

Crossrefs

Not necessarily connected k-regular simple graphs girth exactly 4: A198314 (any k), A185644 (triangle); fixed k: A026797 (k=2), A185134 (k=3), this sequence (k=4).

A185143 (g=3), A185144 (g=4).

Not necessarily connected 4-regular simple graphs with girth exactly g: A185140 (triangle); fixed g: A185143 (g=3), this sequence (g=4).

Sequence in context: A151366 A184944 A033886 * A185344 A237275 A087131

Adjacent sequences: A185141 A185142 A185143 * A185145 A185146 A185147

Keyword

nonn,hard,more

Author

Jason Kimberley, Nov 04 2011

Extensions

Corrected by Jason Kimberley, Jan 03 2013

Status

approved