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A054927 Number of connected unlabeled graphs having n nodes and ceiling(n(n-1)/4) edges such that the complement is also connected. 0
1, 0, 0, 1, 4, 17, 122, 1512, 32692, 1332942, 105327842, 15931236010, 4514847754466, 2400986640234092, 2424697785383015323, 4646743375611622382082, 16785578201380816581985232, 114710315501226850209685442155 (list; graph; refs; listen; history; text; internal format)
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 A032325

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

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Last modified November 21 09:14 EST 2019. Contains 329362 sequences. (Running on oeis4.)