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

Author

Jason Kimberley, Nov 04 2011

Keywords

• nonn
• hard
• more

Links

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

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).

Formula

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

Extensions

Corrected by Jason Kimberley, Jan 03 2013