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A129429 Number of isomorphism classes of 4-regular multigraphs of order n, loops allowed. 9
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; text; internal format)
OFFSET

1,2

COMMENTS

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

LINKS

Table of n, a(n) for n=1..23.

R. C. Read, The enumeration of locally restricted graphs (I), J. London Math. Soc. 34 (1959) 417-436.

FORMULA

Euler transform of A085549. - Andrew Howroyd, Mar 15 2020

CROSSREFS

Column k=4 of A167625.

Cf. A085549, A129418, A129427, A129431, A129433, A129435, A129437.

Sequence in context: A058737 A274478 A238124 * A084204 A030238 A132364

Adjacent sequences:  A129426 A129427 A129428 * A129430 A129431 A129432

KEYWORD

nonn

AUTHOR

Brendan McKay, Apr 15 2007

EXTENSIONS

Using equation (5.8) of Read's paper, new terms a(17)-a(19) were computed in MAGMA by Jason Kimberley, Oct 05 2009

Four more terms a(20)-a(23) also computed by Jason Kimberley, Nov 09 2009

STATUS

approved

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Last modified July 8 03:38 EDT 2020. Contains 335504 sequences. (Running on oeis4.)