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A129429
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Number of isomorphism classes of 4-regular multigraphs of order n, loops allowed.
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9
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1, 3, 7, 20, 56, 187, 654, 2705, 12587, 67902, 417065, 2897432, 22382255, 189930004, 1750561160, 17380043136, 184653542135, 2088649831822, 25046462480066, 317295911519901, 4233450347175663, 59329632953577985, 871281036897298464
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Computed using software at http://cs.anu.edu.au/~bdm/nauty/
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LINKS
| 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), Oct 05 2009]
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FORMULA
| a(n)=N\{S_n[S_4] * S_{2n}[S_2]\} [From Jason Kimberley (Jason.Kimberley(AT)newcastle.edu.au), Oct 05 2009]
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CROSSREFS
| Cf. A085549, A129418, A129427, A129431, A129433, A129435, A129437
Sequence in context: A018034 A000227 A058737 * A084204 A030238 A132364
Adjacent sequences: A129426 A129427 A129428 * A129430 A129431 A129432
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KEYWORD
| nonn
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AUTHOR
| Brendan McKay (bdm(at)cs.anu.edu.au), Apr 15 2007
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EXTENSIONS
| Using equation (5.8) of Read 1959, new terms a(17), a(18) and a(19) were computed in Magma by Jason Kimberley (Jason.Kimberley(AT)newcastle.edu.au), Oct 05 2009
Four more terms a(20)..a(23) also computed by Jason Kimberley (Jason.Kimberley(AT)newcastle.edu.au), Nov 09 2009
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