|
%I M2011 #23 Feb 20 2023 22:08:38
%S 1,1,2,11,171,8603,1478644,870014637
%N Number of unilateral digraphs with n unlabeled nodes.
%D F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 218.
%D Ronald C. Read, email to _N. J. A. Sloane_, 28 August, 2000.
%D R. C. Read and R. J. Wilson, An Atlas of Graphs, Oxford, 1998.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H R. W. Robinson, <a href="http://dx.doi.org/10.1002/jgt.3190010215">Counting strong digraphs (research announcement)</a>, J. Graph Theory 1, 1977, pp. 189-190.
%Y Cf. A057270, A003029 (labeled case), A003085, A035512, A051421, A049531, A049512.
%K nonn,nice,more
%O 0,3
%A _N. J. A. Sloane_
%E Note that Read and Wilson incorrectly give a(4) as 172 - thanks to _Vladeta Jovovic_, Goran Kilibarda for finding this error and for verifying a(5).
%E a(7) from _Sean A. Irvine_, Jan 26 2015
|
