A033886 - OEIS

A033886

Number of connected 4-regular simple graphs on n vertices with girth at least 4.

1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 2, 2, 12, 31, 220, 1606, 16828, 193900, 2452818, 32670330, 456028474, 6636066099, 100135577747, 1582718912968

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,11

COMMENTS

The null graph on 0 vertices is vacuously connected and 4-regular; since it is acyclic, it has infinite girth. - Jason Kimberley, Jan 29 2011

REFERENCES

M. Meringer, Fast Generation of Regular Graphs and Construction of Cages. Journal of Graph Theory, 30 (1999), pp. 137-146.

LINKS

Table of n, a(n) for n=0..23.

Jason Kimberley, Connected regular graphs with girth at least 4

Jason Kimberley, Index of sequences counting connected k-regular simple graphs with girth at least g

M. Meringer, Tables of Regular Graphs

CROSSREFS

Contribution from Jason Kimberley, Mar 19 2010 and Jan 28 2011: (Start)

4-regular simple graphs with girth at least 4: this sequence (connected), A185244 (disconnected), A185344 (not necessarily connected).

Connected k-regular simple graphs with girth at least 4: A186724 (any k), A186714 (triangle); specified degree k: A185114 (k=2), A014371 (k=3), this sequence (k=4), A058275 (k=5), A058276 (k=6), A181153 (k=7), A181154 (k=8), A181170 (k=9).

Connected 4-regular simple graphs with girth at least g: A006820 (g=3), this sequence (g=4), A058343 (g=5), A058348 (g=6).

Connected 4-regular simple graphs with girth exactly g: A184943 (g=3), A184944 (g=4), A184945 (g=5). (End)

Sequence in context: A093044 A151366 A184944 * A185144 A185344 A237275

Adjacent sequences: A033883 A033884 A033885 * A033887 A033888 A033889

KEYWORD

nonn,nice,more,hard

AUTHOR

N. J. A. Sloane, Dec 17 2000

EXTENSIONS

By running M. Meringer's GENREG at U. Newcastle for 6.25, 107 and 1548 processor days, a(21), a(22), and a(23) were completed by Jason Kimberley on Dec 06 2009, Mar 19 2010, and Nov 02 2011.

STATUS

approved