A001231 Number of nonisomorphic projective planes of order n.

1, 1, 1, 1, 0, 1, 1, 4, 0

Offset: 2

Author

N. J. A. Sloane

Keywords

• nonn
• hard
• more
• nice

Comments

The Bruck-Ryser theorem says that a(n)=0 if n == 1 or 2 (mod 4) and is not the sum of two squares.

References

• CRC Handbook of Combinatorial Designs, 1996, p. 695.
• Handbook of Combinatorics, North-Holland '95, p. 672.

Links

• C. W. H. Lam, Publications
• C. W. H. Lam, The Search for a Finite Projective Plane of Order 10, American Mathematical Monthly, 98, (no. 4) 1991, 305 - 318.
• C. W. H. Lam, G. Kolesova and S. Swiercz, A computer search for finite projective planes of order 9, Discrete Math., 92 (1991), 187-195.
• C. W. H. Lam, L. Thiel and S. Swiercz, The non-existence of finite projective planes of order 10, Canad. J. Math., 41 (1989), 1117-1123.
• G. Eric Moorhouse, Projective Planes of Small Order
• N. J. A. Sloane, My favorite integer sequences, in Sequences and their Applications (Proceedings of SETA '98).
• Eric Weisstein's World of Mathematics, Projective Planes