

A186726


Number of connected regular graphs with n nodes and girth at least 6.


13



1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 6, 1, 33, 1, 386, 1, 7575, 1, 181229, 1, 4624503, 1, 122090549, 1, 3328929974, 1, 93990693868, 26, 2754223099408, 13505
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OFFSET

0,15


LINKS

Table of n, a(n) for n=0..37.
Jason Kimberley, Connected regular graphs with girth at least 6
Jason Kimberley, Index of sequences counting connected kregular 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) 137146.


FORMULA

a(n) = sum of the nth row of A186716.


EXAMPLE

a(37) = 0 + 0 + 1 + 0 + 13504 = 13505.


CROSSREFS

Connected regular graphs of any degree with girth at least g: A005177 (g=3), A186724 (g=4), A186725 (g=5), this sequence (g=6), A186727 (g=7), A186728 (g=8), A186729 (g=9).
Connected kregular simple graphs with girth at least 6: this sequence (any k), A186716 (triangle); specific k: A185116 (k=2), A014374 (k=3), A058348 (k=4).
Sequence in context: A225821 A113766 A204992 * A205405 A112623 A130675
Adjacent sequences: A186723 A186724 A186725 * A186727 A186728 A186729


KEYWORD

nonn,more,hard


AUTHOR

Jason Kimberley, Nov 23 2011


EXTENSIONS

a(36)a(37) from Jinyuan Wang, Mar 02 2020


STATUS

approved



