

A014372


Number of trivalent connected simple graphs with 2n nodes and girth at least 5.


21



1, 0, 0, 0, 0, 1, 2, 9, 49, 455, 5783, 90938, 1620479, 31478584, 656783890, 14621871204, 345975648562
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OFFSET

0,7


COMMENTS

The null graph on 0 vertices is vacuously connected and 3regular; since it is acyclic, it has infinite girth.  Jason Kimberley, Jan 29 2011
Brendan McKay has observed that a(13) = 31478584 is output by genreg, minibaum, and snarkhunter, but Meringer's table currently has a(13) = 31478582.  Jason Kimberley, May 17 2017


REFERENCES

CRC Handbook of Combinatorial Designs, 1996, p. 647.


LINKS



CROSSREFS

Contribution from Jason Kimberley, 2010, 2011, and 2012: (Start)
3regular simple graphs with girth at least 5: this sequence (connected), A185235 (disconnected), A185335 (not necessarily connected).


KEYWORD

nonn,more,hard


AUTHOR



EXTENSIONS

Terms a(15) and a(16) appended, from running Meringer's GENREG for 28.7 and 715.2 processor days at U. Ncle., by Jason Kimberley, Jun 28 2010.


STATUS

approved



