

A003069


Number of nnode digraphs with same converse as complement.
(Formerly M1525)


1



1, 1, 2, 6, 20, 88, 632, 8816, 217616, 10240960, 920250720, 155094492288, 48647483234624, 28422244905194880, 31028639315541654400, 63535600643007773309952, 244919299732387943680047360, 1783414099102940635260044486144
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OFFSET

1,3


COMMENTS

From Sean A. Irvine, Feb 05 2015: (Start)
Converse means reversing the direction of every arc.
Complement means every arc not in the original.
The digraph here have no loops and vertices are unlabelled.
Table 1 on p. 200 of Palmer reference erroneously has a(4) = 5. (End)


REFERENCES

E. M. Palmer, Graphical enumeration problems, pp. 187206 of F. Harary, editor, New Directions in the Theory of Graphs. Academic Press, NY, 1973.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS

Sean A. Irvine, Table of n, a(n) for n = 1..36
Sean A. Irvine, Illustration of initial terms


CROSSREFS

Sequence in context: A304932 A293032 A241497 * A079468 A124382 A318813
Adjacent sequences: A003066 A003067 A003068 * A003070 A003071 A003072


KEYWORD

nonn


AUTHOR

N. J. A. Sloane


EXTENSIONS

a(4) corrected and more terms from Sean A. Irvine, Feb 05 2015


STATUS

approved



