

A198314


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


9



0, 0, 0, 0, 1, 0, 1, 0, 4, 1, 8, 3, 37, 33, 335, 1610, 17985, 193911, 2867313, 32674066, 1581626531, 6705889862
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OFFSET

0,9


LINKS

Table of n, a(n) for n=0..21.
Jason Kimberley, Index of sequences counting not necessarily connected kregular simple graphs with girth exactly g


FORMULA

a(n) = A186744(n) + A210714(n).
a(n) = A185314(n)  A185315(n).


CROSSREFS

Not necessarily connected kregular simple graphs girth exactly 4: this sequence (any k), A185644 (triangle); fixed k: A026797 (k=2), A185134 (k=3), A185144 (k=4).
Not necessarily connected regular simple graphs girth exactly g: A198313 (g=3), this sequence (g=4), A198315 (g=5), A198316 (g=6), A198317 (g=7), A198318 (g=8).
Sequence in context: A145917 A201661 A263498 * A105534 A021243 A096051
Adjacent sequences: A198311 A198312 A198313 * A198315 A198316 A198317


KEYWORD

nonn,more,hard


AUTHOR

Jason Kimberley, Dec 12 2012


EXTENSIONS

a(10) corrected from 9 to 8 by Jason Kimberley, Feb 22 2013


STATUS

approved



