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

Author

N. J. A. Sloane, May 24 2000

Keywords

• nonn
• more

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

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

Formula

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

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