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A054916
Number of connected unlabeled regular graphs with n nodes such that complement is also connected.
0
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
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
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