

A002500


Number of selfconverse relations on n points.
(Formerly M1868 N0740)


3



1, 2, 8, 44, 436, 7176, 222368, 12376880, 1302871456, 254079924896, 94287450368768, 65986000800656832, 88430997899765949952, 226039101814259861321856, 1112311767839787173832758784
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OFFSET

0,2


REFERENCES

F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 155, Table 6.6.1.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
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 = 0..50
F. Harary and E. M. Palmer, Enumeration of selfconverse digraphs, Mathematika, 13 (1966), 151157.


FORMULA

Equals A029849*2  A000595. Cf. A002499.


CROSSREFS

Sequence in context: A126101 A308478 A157994 * A002833 A139015 A197996
Adjacent sequences: A002497 A002498 A002499 * A002501 A002502 A002503


KEYWORD

nonn,nice,easy


AUTHOR

N. J. A. Sloane.


EXTENSIONS

In the Encyclopedia of Integer Sequences the n=6 term is given incorrectly as 484256.
Corrected and extended with formula by Christian G. Bower, Jun 15 1998


STATUS

approved



