A002500 Number of self-converse relations on n points.

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

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• nice
• easy

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.

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