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A006927
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Number of connected trivalent graphs with 2n nodes and girth exactly 7.
(Formerly M3086)
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12
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OFFSET
| 12,2
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REFERENCES
| 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
| Jason Kimberley, Index of sequences counting connected k-regular simple graphs with girth exactly g
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FORMULA
| a(n) = A014375(n) - A014376(n).
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CROSSREFS
| 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).
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: A120603 A139224 A032469 * A014375 A135748 A145386
Adjacent sequences: A006924 A006925 A006926 * A006928 A006929 A006930
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KEYWORD
| nonn,hard,more
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| 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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