A014375 Number of trivalent connected simple graphs with 2n nodes and girth at least 7.

1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 3, 21, 546, 30368, 1782840, 95079083, 4686063120, 220323447962, 10090653722861

Offset

0,14

Comments

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]

References

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

Links

Table of n, a(n) for n=0..21.

Jason Kimberley, Connected regular graphs with girth at least 7

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

M. Meringer, Tables of Regular Graphs

M. Meringer, Fast generation of regular graphs and construction of cages, J. Graph Theory 30 (2) (1999) 137-146. [Jason Kimberley, May 29 2010]

Formula

a(n) = A006927(n) + A014376(n).

Crossrefs

From Jason Kimberley, May 29 2010 and Jan 29 2011: (Start)

Connected k-regular simple graphs with girth at least 7: A186727 (any k), A186717 (triangle); specific k: A185117 (k=2), this sequence (k=3).

Trivalent simple graphs with girth at least g: A185131 (triangle); chosen g: A002851 (g=3), A014371 (g=4), A014372 (g=5), A014374 (g=6), this sequence (g=7), A014376 (g=8).

Trivalent simple graphs with girth exactly g: A198303 (triangle); chosen g: A006923 (g=3), A006924 (g=4), A006925 (g=5), A006926 (g=6), A006927 (g=7). (End)

Sequence in context: A139224 A032469 A006927 * A135748 A145386 A344260

Adjacent sequences: A014372 A014373 A014374 * A014376 A014377 A014378

Keyword

nonn

Author

N. J. A. Sloane.

Extensions

Terms a(17), a(18), and a(19) found by running Meringer's GENREG for 1.9 hours, 99.6 hours, and 207.8 processor days, at U. Ncle., by Jason Kimberley, May 29 2010

Terms a(20) and a(21) from House of Graphs via Jason Kimberley, May 21 2017

Status

approved