A001201 Number of Steiner triple systems (STS's) on 6n+1 or 6n+3 elements. (Formerly M5214 N2268)

1, 1, 30, 840, 1197504000, 60281712691200, 1348410350618155344199680000

Offset

0,3

Comments

To be precise, for n even, a(n) is the number of STS's on 3n+1 elements, and for n odd, a(n) is the number of STS's on 3n elements. - Franklin T. Adams-Watters, Apr 10 2010

References

L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 304.

CRC Handbook of Combinatorial Designs, 1996, p. 70.

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

Table of n, a(n) for n=0..6.

Petteri Kaski and Patric R. J. Östergård, The Steiner triple systems of order 19, Math. Comp. 73 (2004), 2075-2092.

Index entries for sequences related to Steiner systems

Example

There are 1197504000 STS's on 13 elements.

Crossrefs

Indexed by A047241. Cf. A030128, A030129, A051390.

Sequence in context: A049394 A143169 A256324 * A367333 A007850 A162833

Adjacent sequences: A001198 A001199 A001200 * A001202 A001203 A001204

Keyword

nonn,nice,hard,more

Author

N. J. A. Sloane

Status

approved