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 A006924 Number of connected trivalent graphs with 2n nodes and girth exactly 4. (Formerly M1526) 18
 0, 0, 0, 1, 2, 5, 20, 101, 743, 7350, 91763, 1344782, 22160335, 401278984, 7885687604, 166870266608, 3781101495300 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 REFERENCES CRC Handbook of Combinatorial Designs, 1996, p. 647. Gordon Royle, personal communication. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS F. C. Bussemaker, S. Cobeljic, L. M. Cvetkovic and J. J. Seidel, Computer investigations of cubic graphs, T.H.-Report 76-WSK-01, Technological University Eindhoven, Dept. Mathematics, 1976. FORMULA a(n) = A014371(n) - A014372(n). CROSSREFS Connected k-regular simple graphs with girth exactly 4: this sequence (k=3), A184944 (k=4), A184954 (k=5), A184964 (k=6), A184974 (k=7). Connected 3-regular simple graphs with girth exactly g: A198303 (triangle); specified g: A006923 (g=3), this sequence (g=4), A006925 (g=5), A006926 (g=6), A006927 (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: A039909 A009551 A323274 * A212580 A261779 A227096 Adjacent sequences:  A006921 A006922 A006923 * A006925 A006926 A006927 KEYWORD nonn,hard,more AUTHOR EXTENSIONS Definition corrected to include "connected", and "girth at least 4" minus "girth at least 5" formula provided by Jason Kimberley, Dec 12 2009 STATUS approved

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Last modified March 22 23:04 EDT 2019. Contains 321422 sequences. (Running on oeis4.)