The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A006927 Number of connected trivalent graphs with 2n nodes and girth exactly 7. (Formerly M3086) 13
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 3, 21, 545, 30368, 1782839, 95079080, 4686063107 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,14 REFERENCES Gordon Royle, personal communication. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS FORMULA a(n) = A014375(n) - A014376(n). CROSSREFS Connected 3-regular simple graphs with girth exactly g: A198303 (triangle); specified g: A006923 (g=3), A006924 (g=4), A006925 (g=5), A006926 (g=6), this sequence (g=7). Connected 3-regular 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: A285380 A139224 A032469 * A014375 A135748 A145386 Adjacent sequences:  A006924 A006925 A006926 * A006928 A006929 A006930 KEYWORD nonn,hard,more AUTHOR EXTENSIONS Definition amended to include "connected" (no disconnected yet), and "girth at least 7" minus "girth at least 8" formula provided by Jason Kimberley, Dec 12 2009 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified April 16 05:20 EDT 2021. Contains 343030 sequences. (Running on oeis4.)