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A054918 Number of connected unlabeled digraphs with n nodes such that complement is also connected. 1
1, 1, 10, 180, 9120, 1520742, 878908844, 1791588717764, 13024366540532952, 341234368845828951004, 32522226812040344643993088, 11366680383641301437820379768750, 14669062959091969068110415719779627436 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

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*A003085(n) - A000273(n).

MATHEMATICA

A000273 = Cases[Import["https://oeis.org/A000273/b000273.txt", "Table"], {_, _}][[All, 2]];

A003085 = Cases[Import["https://oeis.org/A003085/b003085.txt", "Table"], {_, _}][[All, 2]];

a[n_] := 2*A003085[[n]] - A000273[[n + 1]];

Array[a, 50] (* Jean-Fran├žois Alcover, Aug 31 2019 *)

CROSSREFS

Cf. A000273, A003085.

Sequence in context: A034908 A030048 A318796 * A095807 A064092 A171513

Adjacent sequences:  A054915 A054916 A054917 * A054919 A054920 A054921

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, May 24 2000

EXTENSIONS

More terms from Vladeta Jovovic, Jul 19 2000

STATUS

approved

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Last modified February 18 09:39 EST 2020. Contains 332011 sequences. (Running on oeis4.)