%I #27 Feb 16 2025 08:32:37

%S 1,1,1,5,83,5048,1047008,705422362,1580348371788,12139024825260556,

%T 328160951349343885604,31831080872412589394328804,

%U 11234274997368899732057135454531,14576252633139820879894296847900227082

%N Number of unlabeled strongly connected digraphs with n nodes.

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

%D V. A. Liskovets, A contribution to the enumeration of strongly connected digraphs, Dokl. AN BSSR, 17 (1973), 1077-1080, MR49#4849.

%D R. C. Read and R. J. Wilson, An Atlas of Graphs, Oxford, 1998.

%D R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1976.

%H Andrew Howroyd, <a href="/A035512/b035512.txt">Table of n, a(n) for n = 0..50</a> (terms 0..18 from R. W. Robinson)

%H A. M. Hinz, S. Klavžar, U. Milutinović, C. Petr, <a href="http://dx.doi.org/10.1007/978-3-0348-0237-6">The Tower of Hanoi - Myths and Maths</a>, Birkhäuser 2013. See page 251. <a href="http://tohbook.info">Book's website</a>

%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/StronglyConnectedDigraph.html">Strongly Connected Digraph.</a>

%o (PARI) \\ See PARI link in A350489 for program code.

%o A035512seq(15) \\ _Andrew Howroyd_, Jan 13 2022

%Y The labeled version is A003030.

%Y Row sums of A057276.

%Y Column sums of A350753.

%Y Cf. A003085, A049387, A350489, A350752.

%K nonn,nice,changed

%O 0,4

%A Ronald C. Read

%E a(12) and a(13) added by _N. J. A. Sloane_ from the Robinson report, Oct 17 2006