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Search: id:A129427
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| A129427 |
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Number of isomorphism classes of 3-regular multigraphs of order 2n, loops allowed. |
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+0
9
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| 2, 8, 31, 140, 722, 4439, 32654, 289519, 3054067, 37584620, 527968286, 8308434931, 144345554051, 2738280739075, 56245013793246, 1242596591479816
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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a(1)..a(11) computed using software at http://cs.anu.edu.au/~bdm/nauty/
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LINKS
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R. C. Read, The enumeration of locally restricted graphs (I), J. London Math. Soc. 34 (1959) 417-436. [From Jason Kimberley (Jason.Kimberley(AT)newcastle.edu.au), Sep 17 2009]
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FORMULA
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a(n)=N\{S_{2n}[S_3] * S_{3n}[S_2]\} [From Jason Kimberley (Jason.Kimberley(AT)newcastle.edu.au), Sep 17 2009]
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CROSSREFS
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Cf. A005967, A129416, A129429, A129431, A129433, A129435, A129437
Sequence in context: A009567 A150819 A003175 this_sequence A150820 A150821 A150822
Adjacent sequences: A129424 A129425 A129426 this_sequence A129428 A129429 A129430
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KEYWORD
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nonn,new
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AUTHOR
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Brendan McKay (bdm(at)cs.anu.edu.au), Apr 15 2007
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EXTENSIONS
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Using equation (5.8) of Read 1959, new terms a(12) and a(13) were computed in Magma by Jason Kimberley (Jason.Kimberley(AT)newcastle.edu.au), Sep 17 2009
Further terms a(14),a(15),a(16) also computed by Jason Kimberley, announced Nov 09 2009
Formula corrected from n vertices to 2n vertices by Jason Kimberley (Jason.Kimberley(AT)newcastle.edu.au), Nov 09 2009
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