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Number of connected unlabeled graphs having n nodes and ceiling(n(n-1)/4) edges such that the complement is also connected.
0

%I #24 May 08 2019 10:43:54

%S 1,0,0,1,4,17,122,1512,32692,1332942,105327842,15931236010,

%T 4514847754466,2400986640234092,2424697785383015323,

%U 4646743375611622382082,16785578201380816581985232,114710315501226850209685442155

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

%C 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

%H V. A. Liskovets, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL3/LISK/Derseq.html">Some easily derivable sequences</a>, J. Integer Sequences, 3 (2000), #00.2.2.

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

%K nonn,more

%O 1,5

%A _N. J. A. Sloane_, May 24 2000

%E Name changed by _Brendan McKay_, Apr 14 2019

%E 3 more terms by lookup in the 3 seqs of the formula. - _R. J. Mathar_, May 08 2019