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A051421 Number of digraphs on n unlabeled nodes with a sink (or, with a source). 6

%I

%S 1,1,2,12,185,8990,1505939,875542491

%N Number of digraphs on n unlabeled nodes with a sink (or, with a source).

%C Here a sink is defined to be a node to which all other nodes have a directed path. - _Andrew Howroyd_, Dec 27 2021

%D F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 218 (incorrect version).

%D R. C. Read (rcread(AT)math.uwaterloo.ca), email to _N. J. A. Sloane_, 28 August, 2000.

%Y The labeled case is A003028.

%Y Cf. A049531.

%K nonn,nice,more

%O 0,3

%A _Vladeta Jovovic_

%E a(6) corrected and a(7) from _Sean A. Irvine_, Sep 11 2021

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Last modified January 20 00:45 EST 2022. Contains 350467 sequences. (Running on oeis4.)