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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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13
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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
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OFFSET
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1,2
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COMMENTS
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Initial terms computed using software at http://users.cecs.anu.edu.au/~bdm/nauty/
Equation (5.8) of Read's paper tells us a(n) = N {S_n[S_4] * S_{2n}[S_2]}, where we are working with cycle index polynomials. - Jason Kimberley, Oct 05 2009
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LINKS
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FORMULA
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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Using equation (5.8) of Read's paper, new terms a(17)-a(19) were computed in MAGMA by Jason Kimberley, Oct 05 2009
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STATUS
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approved
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