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A054914 Number of labeled connected digraphs with n nodes such that complement is also connected. 1
1, 2, 44, 3572, 1005584, 1060875152, 4382913876704, 71987098738435232, 4721068803628864289024, 1237845578934919489219757312, 1298046978912816702510086132201984, 5444486716626952189940499391640815580672, 91343710775311761525117954724021374685703481344 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Alois P. Heinz, 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*A003027(n) - A053763(n).

MAPLE

b:= n-> 2^(n^2-n):

g:= proc(n) option remember; local k; `if`(n=0, 1,

      b(n)- add(k*binomial(n, k) *b(n-k)*g(k), k=1..n-1)/n)

    end:

a:= n-> 2*g(n)-b(n):

seq (a(n), n=1..20);  # Alois P. Heinz, Oct 21 2012

MATHEMATICA

nn=20; g=Sum[2^(2Binomial[n, 2])x^n/n!, {n, 0, nn}]; Drop[Range[0, nn]!CoefficientList[Series[2(Log[g]+1)-g, {x, 0, nn}], x], 1]  (* Geoffrey Critzer, Oct 21 2012 *)

CROSSREFS

Sequence in context: A054732 A161722 A290879 * A329021 A275307 A291808

Adjacent sequences:  A054911 A054912 A054913 * A054915 A054916 A054917

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 May 25 08:26 EDT 2020. Contains 334585 sequences. (Running on oeis4.)