This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A006923 M2944 #28 Sep 28 2023 02:05:22 %S A006923 0,0,1,1,3,13,63,399,3268,33496,412943,5883727,94159721,1661723296, %T A006923 31954666517,663988090257,14814445040728 %N A006923 Number of connected trivalent graphs with 2n nodes and with girth exactly 3. %D A006923 CRC Handbook of Combinatorial Designs, 1996, p. 647. %D A006923 Gordon Royle, personal communication. %D A006923 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A006923 F. C. Bussemaker, S. Cobeljic, L. M. Cvetkovic and J. J. Seidel, <a href="http://alexandria.tue.nl/repository/books/252909.pdf">Computer investigations of cubic graphs</a>, T.H.-Report 76-WSK-01, Technological University Eindhoven, Dept. Mathematics, 1976. %H A006923 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 A006923 a(n) = A002851(n) - A014371(n). %Y A006923 Connected 3-regular simple graphs with girth exactly g: A198303 (triangle); specified g: this sequence (g=3), A006924 (g=4), A006925 (g=5), A006926 (g=6), A006927 (g=7). %Y A006923 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 A006923 nonn,hard,more %O A006923 0,5 %A A006923 _N. J. A. Sloane_ %E A006923 Definition corrected to include "connected", and "girth at least 3" minus "girth at least 4" formula provided by _Jason Kimberley_, Dec 12 2009 %E A006923 Terms a(14), a(15), and a(16) appended using "new" terms of A014371 by _Jason Kimberley_, Nov 16 2011