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 A006927 Number of connected trivalent graphs with 2n nodes and girth exactly 7. (Formerly M3086) 13

%I M3086

%S 0,0,0,0,0,0,0,0,0,0,0,0,1,3,21,545,30368,1782839,95079080,4686063107

%N Number of connected trivalent graphs with 2n nodes and girth exactly 7.

%D Gordon Royle, personal communication.

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H Jason Kimberley, <a href="/wiki/User:Jason_Kimberley/C_k-reg_girth_eq_g_index">Index of sequences counting connected k-regular simple graphs with girth exactly g</a>

%F a(n) = A014375(n) - A014376(n).

%Y 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).

%Y 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).

%K nonn,hard,more

%O 0,14

%A _N. J. A. Sloane_.

%E 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

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Last modified May 6 16:14 EDT 2021. Contains 343586 sequences. (Running on oeis4.)