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A054954 Number of unlabeled semi-strong digraphs on n nodes with an even number of pairwise different components. 4
0, 0, 1, 5, 88, 5141, 1052471, 706498013, 1581059448184, 12140608800384871, 328173098339746387013, 31831409094194340869533850, 11234306830091593156638822493531, 14576263867574000953696306880725802283 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,4
LINKS
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
Sequence in context: A300135 A221465 A184239 * A266064 A106971 A136618
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

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Last modified March 28 22:04 EDT 2024. Contains 371254 sequences. (Running on oeis4.)