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A001231 Number of nonisomorphic projective planes of order n. 2
1, 1, 1, 1, 0, 1, 1, 4, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET
2,8
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.
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
CROSSREFS
Sequence in context: A058473 A115527 A050920 * A089418 A274981 A124856
KEYWORD
nonn,hard,more,nice
AUTHOR
STATUS
approved

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Last modified March 19 03:21 EDT 2024. Contains 370952 sequences. (Running on oeis4.)