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A054953
Number of unlabeled semi-strong digraphs on n nodes with an odd number of pairwise different components.
4
1, 1, 5, 83, 5048, 1047013, 705422455, 1580348377261, 12139024826336632, 328160951350054991463, 31831080872414173375174213, 11234274997368911879051177335450, 14576252633139821208116086572516525403, 70075713785837731364265242597960381223077163
OFFSET
1,3
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 = -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
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