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A054941 Number of connected oriented graphs on n labeled nodes. 8
1, 2, 20, 624, 55248, 13982208, 10358360640, 22792648882176, 149888345786341632, 2952810709943411146752, 174416705255313941476193280, 30901060796613886817249881227264, 16422801513633911416125344647746244608, 26183660776604240464418800095675915958222848 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The triangle of oriented labeled graphs on n>=1 nodes with 1<=k<=n components and row sums A047656 starts:

       1;

       2,      1;

      20,      6,     1;

     624,     92,    12,   1;

   55248,   3520,   260,  20,  1;

13982208, 354208, 11880, 580, 30, 1; - R. J. Mathar, Apr 29 2019

LINKS

Seiichi Manyama, Table of n, a(n) for n = 1..65

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

FORMULA

E.g.f.: log( Sum_{n >= 0} 3^binomial(n, 2)*x^n/n! ). - Vladeta Jovovic, Feb 14 2003

MATHEMATICA

nn=20; s=Sum[3^Binomial[n, 2]x^n/n!, {n, 0, nn}]; Drop[Range[0, nn]! CoefficientList[Series[Log[s]+1, {x, 0, nn}], x], 1] (* Geoffrey Critzer, Oct 22 2012 *)

PROG

(PARI) N=20; x='x+O('x^N); Vec(serlaplace(log(sum(k=0, N, 3^binomial(k, 2)*x^k/k!)))) \\ Seiichi Manyama, May 18 2019

CROSSREFS

Cf. A001187, A003027.

Sequence in context: A197743 A009182 A015207 * A012495 A168480 A198761

Adjacent sequences:  A054938 A054939 A054940 * A054942 A054943 A054944

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, May 24 2000

EXTENSIONS

More terms from Vladeta Jovovic, Feb 14 2003

STATUS

approved

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Last modified July 11 23:51 EDT 2020. Contains 335654 sequences. (Running on oeis4.)