A054927 Number of connected unlabeled graphs having n nodes and ceiling(n(n-1)/4) edges such that the complement is also connected.

1, 0, 0, 1, 4, 17, 122, 1512, 32692, 1332942, 105327842, 15931236010, 4514847754466, 2400986640234092, 2424697785383015323, 4646743375611622382082, 16785578201380816581985232, 114710315501226850209685442155

Offset

1,5

Comments

These graphs are called "median graphs" by Liskovets, but that name is more commonly used for the graphs counted in A292623. - Brendan McKay, Apr 14 2019

Links

Table of n, a(n) for n=1..18.

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

Formula

a(n) = A001437(n)+A054926(n)-A000717(n).

Crossrefs

Sequence in context: A206353 A260694 A032115 * A307794 A071138 A337521

Adjacent sequences: A054924 A054925 A054926 * A054928 A054929 A054930

Keyword

nonn,more

Author

N. J. A. Sloane, May 24 2000

Extensions

Name changed by Brendan McKay, Apr 14 2019

3 more terms by lookup in the 3 seqs of the formula. - R. J. Mathar, May 08 2019

Status

approved