A129416 - OEIS

A129416

Number of isomorphism classes of 3-regular loopless multigraphs of order 2n.

1, 3, 9, 32, 135, 709, 4637, 38374, 391473, 4764778, 66913591, 1056886475, 18446472265, 351482430368, 7247888726269, 160671989129665, 3808499268504548, 96094161981827499, 2570930535917564366, 72688753062897675445

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OFFSET

1,2

COMMENTS

Initial terms computed using software at http://users.cecs.anu.edu.au/~bdm/nauty/

LINKS

Table of n, a(n) for n=1..20.

L. Travis, Graphical Enumeration: A Species-Theoretic Approach, arXiv:math/9811127 [math.CO], 1998.; Ph.D. thesis, Brandeis University, 1999, Section 4.3.

FORMULA

Euler transform of A000421.

CROSSREFS

Column k=3 of A333330.

Cf. A000421 (connected, inv. Eul. trans.), A129427, A129418, A129420, A129422, A129424, A129426.

Sequence in context: A324238 A005964 A246138 * A210689 A334642 A273596

Adjacent sequences: A129413 A129414 A129415 * A129417 A129418 A129419

KEYWORD

nonn

AUTHOR

Brendan McKay, Apr 15 2007

EXTENSIONS

a(13)-a(20) from Andrew Howroyd, Mar 19 2020

STATUS

approved