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

Author

N. J. A. Sloane, May 23 2000

Keywords

• nonn
• hard

Links

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

Crossrefs

Cf. A005176, A005177, A068932.

Formula

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

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