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A054951
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Number of unlabeled semi-strong digraphs on n nodes with mutually nonisomorphic components.
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3
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1, 1, 4, 78, 4960, 1041872, 704369984, 1579641879248, 12137443766888448, 328148810741254606592, 31830752699315833628787200, 11234243165959817684710307801600, 14576241398832991116522929933694031872, 70075699209573863790264288901653500497274880
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OFFSET
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1,3
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REFERENCES
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V. A. Liskovets, A contribution to the enumeration of strongly connected digraphs, Dokl. AN BSSR, 17 (1973), 1077-1080 (Russian), MR49#4849.
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LINKS
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Table of n, a(n) for n=1..14.
V. A. Liskovets, Some easily derivable sequences, J. Integer Sequences, 3 (2000), #00.2.2.
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FORMULA
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G.f.: 1 - Product_{n > 0} (1 - x^n)^A035512(n). - Andrew Howroyd, Sep 10 2018
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MATHEMATICA
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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 *)
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CROSSREFS
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Cf. A035512, A049387, A054952, A054953, A054954.
Sequence in context: A220240 A246606 A210903 * A215843 A048957 A006425
Adjacent sequences: A054948 A054949 A054950 * A054952 A054953 A054954
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KEYWORD
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nonn,easy
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AUTHOR
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N. J. A. Sloane, May 24 2000
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EXTENSIONS
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More terms from Vladeta Jovovic, Mar 11 2003
a(12)-a(14) from Andrew Howroyd, Sep 10 2018
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STATUS
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approved
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