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Number of n-node digraphs with same converse as complement.
(Formerly M1525)
1

%I M1525 #17 Feb 06 2015 07:11:25

%S 1,1,2,6,20,88,632,8816,217616,10240960,920250720,155094492288,

%T 48647483234624,28422244905194880,31028639315541654400,

%U 63535600643007773309952,244919299732387943680047360,1783414099102940635260044486144

%N Number of n-node digraphs with same converse as complement.

%C From _Sean A. Irvine_, Feb 05 2015: (Start)

%C Converse means reversing the direction of every arc.

%C Complement means every arc not in the original.

%C The digraph here have no loops and vertices are unlabelled.

%C Table 1 on p. 200 of Palmer reference erroneously has a(4) = 5. (End)

%D E. M. Palmer, Graphical enumeration problems, pp. 187-206 of F. Harary, editor, New Directions in the Theory of Graphs. Academic Press, NY, 1973.

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H Sean A. Irvine, <a href="/A003069/b003069.txt">Table of n, a(n) for n = 1..36</a>

%H Sean A. Irvine, <a href="/A003069/a003069.png">Illustration of initial terms</a>

%K nonn

%O 1,3

%A _N. J. A. Sloane_

%E a(4) corrected and more terms from _Sean A. Irvine_, Feb 05 2015