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A185134
Number of, not necessarily connected, 3-regular simple graphs on 2n vertices with girth exactly 4.
12
0, 0, 0, 1, 2, 5, 21, 103, 752, 7385, 91939, 1345933, 22170664, 401399440, 7887389438, 166897766824, 3781593764772
OFFSET
0,5
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
KEYWORD
nonn,hard,more
AUTHOR
Jason Kimberley, Mar 21 2012
STATUS
approved