A098702 Number of self-polar configurations of type (n_3).

0, 0, 0, 0, 0, 0, 1, 1, 3, 10, 25, 95, 365, 1432, 5799, 24092, 102413, 445363, 1991320

Offset

1,9

Links

Table of n, a(n) for n=1..19.

A. Betten, G. Brinkmann and T. Pisanski, Counting symmetric configurations v_3, Discrete Appl. Math., 99 (2000), 331-338.

M. Boben et al., Small triangle-free configurations of points and lines, Discrete Comput. Geom., 35 (2006), 405-427.

T. Pisanski, M. Boben, D. Marušic, A. Orbanic, A. Graovac, The 10-cages and derived configurations, Discrete Math. 275 (2004), 265-276.

Example

Example: the Fano plane is the only 7_3 configuration and it is self-polar.

Crossrefs

Cf. A001403, A023994.

Sequence in context: A196984 A131433 A110713 * A100001 A227937 A299754

Adjacent sequences: A098699 A098700 A098701 * A098703 A098704 A098705

Keyword

nonn,nice,hard

Author

N. J. A. Sloane, Nov 05 2004

Extensions

a(1)-a(18) from the Betten, Brinkmann and Pisanski article.

a(19) from the Pisanski et al. article.

Status

approved