A054954 Number of unlabeled semi-strong digraphs on n nodes with an even number of pairwise different components.

0, 0, 1, 5, 88, 5141, 1052471, 706498013, 1581059448184, 12140608800384871, 328173098339746387013, 31831409094194340869533850, 11234306830091593156638822493531, 14576263867574000953696306880725802283

Offset

1,4

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) = (A054952(n) - A054951(n))/2. - Andrew Howroyd, Sep 10 2018

Mathematica

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

Crossrefs

Cf. A054951, A054952, A054953.

Sequence in context: A300135 A221465 A184239 * A266064 A106971 A136618

Adjacent sequences: A054951 A054952 A054953 * A054955 A054956 A054957

Keyword

nonn,easy

Author

N. J. A. Sloane, May 24 2000

Extensions

More terms from Vladeta Jovovic, Mar 11 2003

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

Status

approved