

A006925


Number of connected trivalent graphs with 2n nodes and girth exactly 5.
(Formerly M1879)


16



0, 0, 0, 0, 0, 1, 2, 8, 48, 450, 5751, 90553, 1612905, 31297357, 652159389, 14499780660, 342646718608
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OFFSET

0,7


REFERENCES

CRC Handbook of Combinatorial Designs, 1996, p. 647.
Gordon Royle, personal communication.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS

Table of n, a(n) for n=0..16.
Jason Kimberley, Index of sequences counting connected kregular simple graphs with girth exactly g


FORMULA

a(n) = A014372(n)  A014374(n).


CROSSREFS

Connected kregular simple graphs with girth exactly 5: this sequence (k=3), A184945 (k=4), A184955 (k=5).
Connected 3regular simple graphs with girth exactly g: A198303 (triangle); specified g: A006923 (g=3), A006924 (g=4), this sequence
(g=5), A006926 (g=6), A006927 (g=7).
Connected 3regular simple graphs with girth at least g: A002851 (g=3), A014371 (g=4), A014372 (g=5), A014374 (g=6), A014375 (g=7), A014376 (g=8).
Sequence in context: A177386 A112541 A052667 * A185135 A238805 A005867
Adjacent sequences: A006922 A006923 A006924 * A006926 A006927 A006928


KEYWORD

nonn,hard,more


AUTHOR

N. J. A. Sloane.


EXTENSIONS

Definition corrected to include "connected", and "girth at least 5" minus "girth at least 6" formula provided by Jason Kimberley, Dec 12 2009


STATUS

approved



