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A054915 Number of unlabeled connected graphs with n nodes such that complement is also connected. 1
1, 0, 0, 1, 8, 68, 662, 9888, 247492, 11427974, 994403266, 163028488360, 50169784370486, 28952819268460634, 31368276315718175152, 63938104521922794457626, 245807799210635120355337360, 1787085725352186477232522962312, 24634233605674730786262294027930520 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..50

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

FORMULA

a(n) = 2*A001349(n) - A000088(n).

MATHEMATICA

nn = 15; Clear[g, c, a, b]; c[z_] := Sum[a[n] z^n, {n, 1, nn}];

g[z_] := Sum[NumberOfGraphs[n] z^n, {n, 0, nn}]; sol =

SolveAlways[ 0 == Series[g[z] - Product[1/(1 - z^i)^a[i], {i, 1, nn}], {z, 0, nn}], z]; 2*(Flatten[Table[a[n], {n, 1, nn}] /. sol]) - (Drop[

CoefficientList[Series[g[z], {z, 0, nn + 1}], z], 1]) (* Geoffrey Critzer, Aug 12 2016 *)

CROSSREFS

Cf. A000088, A001349.

Sequence in context: A068766 A233736 A279266 * A073555 A167859 A243246

Adjacent sequences:  A054912 A054913 A054914 * A054916 A054917 A054918

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, May 23 2000

EXTENSIONS

More terms from Vladeta Jovovic, Jul 17 2000

STATUS

approved

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Last modified March 31 19:37 EDT 2020. Contains 333151 sequences. (Running on oeis4.)