A054952 Number of unlabeled semi-strong digraphs on n nodes with pairwise different components.

1, 1, 6, 88, 5136, 1052154, 706474926, 1581054875274, 12140605885784816, 328173091958855376334, 31831409045512513121561226, 11234306828778006073392046869300, 14576263867446651299709243211339018934, 70075728362101598938266196294267261948879446

Offset: 1

Author

N. J. A. Sloane, May 24 2000

Keywords

• nonn
• easy

Comments

Weigh transform of A035512. - Andrew Howroyd, Sep 10 2018

A digraph is semi-strong if all its weakly connected components are strongly connected. - Andrew Howroyd, Jan 14 2022

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.

Crossrefs

Cf. A035512, A054951, A054953, A054954.

Programs

Mathematica

m = 15;
A035512 = Cases[Import["https://oeis.org/A035512/b035512.txt", "Table"], {, }][[All, 2]];
gf = -1 + Product[(1 + x^n)^A035512[[n + 1]], {n, 1, m}];
CoefficientList[gf + O[x]^m , x] // Rest (* Jean-François Alcover, Aug 26 2019, after Andrew Howroyd *)

Formula

G.f.: -1 + Product_{n > 0} (1 + x^n)^A035512(n). - Andrew Howroyd, Sep 10 2018

Extensions

More terms from Vladeta Jovovic, Mar 11 2003

a(12)-a(14) from Andrew Howroyd, Sep 10 2018