A185134 Number of, not necessarily connected, 3-regular simple graphs on 2n vertices with girth exactly 4.

0, 0, 0, 1, 2, 5, 21, 103, 752, 7385, 91939, 1345933, 22170664, 401399440, 7887389438, 166897766824, 3781593764772

Offset

0,5

Links

Table of n, a(n) for n=0..16.

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

Formula

a(n) = A185334(n) - A185335(n).

a(n) = A006924(n) + A185034(n).

Crossrefs

Not necessarily connected k-regular simple graphs girth exactly 4: A198314 (any k), A185644 (triangle); fixed k: A026797 (k=2), this sequence (k=3), A185144 (k=4).

Not necessarily connected 3-regular simple graphs on 2n vertices with girth exactly g: A185130 (triangle); fixed g: A185133 (g=3), this sequence (g=4), A185135 (g=5), A185136 (g=6).

Sequence in context: A115087 A008981 A008982 * A347497 A130471 A002628

Adjacent sequences: A185131 A185132 A185133 * A185135 A185136 A185137

Keyword

nonn,hard,more

Author

Jason Kimberley, Mar 21 2012

Status

approved