A054916 Number of connected unlabeled regular graphs with n nodes such that complement is also connected.

1, 0, 0, 0, 1, 2, 2, 12, 18, 158, 532, 18956, 389418, 50314722, 2942198334, 1698517035792, 442786966113484, 649978211591577760, 429712868499646362046, 2886054228478618206288948, 8835589045148342277740379344, 152929279364927228928017067050204, 1207932509391069805495173186013097090, 99162609848561525198669168626676490270856

Offset

1,6

Links

Table of n, a(n) for n=1..24.

V. A. Liskovets, Some easily derivable sequences, J. Integer Sequences, 3 (2000), #00.2.2.

Formula

a(n) = 2*A005177(n)-A005176(n) = A005177(n)-A068932(n).

Crossrefs

Cf. A005176, A005177, A068932.

Sequence in context: A059187 A350329 A265458 * A194767 A302368 A346757

Adjacent sequences: A054913 A054914 A054915 * A054917 A054918 A054919

Keyword

nonn,hard

Author

N. J. A. Sloane, May 23 2000

Extensions

Terms a(11)-a(16) appended, journal link changed to article link, and second formula included, by Jason Kimberley, Oct 24 2009

a(17)-a(24) from Andrew Howroyd, May 19 2020

Status

approved