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A006925
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Number of connected trivalent graphs with 2n nodes and girth exactly 5.
(Formerly M1879)
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16
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0, 0, 0, 0, 0, 1, 2, 8, 48, 450, 5751, 90553, 1612905, 31297357, 652159389, 14499780660, 342646718608
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OFFSET
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0,7
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REFERENCES
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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).
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LINKS
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FORMULA
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CROSSREFS
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Connected k-regular simple graphs with girth exactly 5: this sequence (k=3), A184945 (k=4), A184955 (k=5).
Connected 3-regular simple graphs with girth exactly g: A198303 (triangle); specified g: A006923 (g=3), A006924 (g=4), this sequence
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KEYWORD
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nonn,hard,more
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AUTHOR
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EXTENSIONS
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Definition corrected to include "connected", and "girth at least 5" minus "girth at least 6" formula provided by Jason Kimberley, Dec 12 2009
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STATUS
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approved
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