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A014372
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Number of trivalent connected simple graphs with 2n nodes and girth at least 5.
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21
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1, 0, 0, 0, 0, 1, 2, 9, 49, 455, 5783, 90938, 1620479, 31478584, 656783890, 14621871204, 345975648562
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OFFSET
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0,7
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COMMENTS
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The null graph on 0 vertices is vacuously connected and 3-regular; 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
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REFERENCES
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CRC Handbook of Combinatorial Designs, 1996, p. 647.
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LINKS
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CROSSREFS
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Contribution from Jason Kimberley, 2010, 2011, and 2012: (Start)
3-regular simple graphs with girth at least 5: this sequence (connected), A185235 (disconnected), A185335 (not necessarily connected).
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KEYWORD
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nonn,more,hard
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AUTHOR
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EXTENSIONS
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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.
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STATUS
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approved
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