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 A054941 Number of weakly connected oriented graphs on n labeled nodes. 10
 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 Row sums of A350732. The unlabeled version is A086345. Cf. A001187 (graphs), A003027 (digraphs), A350730 (strongly connected). 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 March 26 13:22 EDT 2023. Contains 361549 sequences. (Running on oeis4.)