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A002500 Number of self-converse relations on n points.
(Formerly M1868 N0740)
3
1, 2, 8, 44, 436, 7176, 222368, 12376880, 1302871456, 254079924896, 94287450368768, 65986000800656832, 88430997899765949952, 226039101814259861321856, 1112311767839787173832758784 (list; graph; refs; listen; history; text; internal format)
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 self-converse digraphs, Mathematika, 13 (1966), 151-157.

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

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Last modified January 20 09:40 EST 2021. Contains 340302 sequences. (Running on oeis4.)