login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual Appeal: Today, Nov 11 2014, is the 4th anniversary of the launch of the new OEIS web site. 70,000 sequences have been added in these four years, all edited by volunteers. Please make a donation (tax deductible in the US) to help keep the OEIS running.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A001201 Steiner triple systems (STS's) on 6n+1 or 6n+3 elements.
(Formerly M5214 N2268)
8
1, 1, 30, 840, 1197504000, 60281712691200, 1348410350618155344199680000 (list; graph; refs; listen; history; text; internal format)
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.

P. Kaski and P. 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: A160269 A049394 A143169 * A007850 A162833 A163208

Adjacent sequences:  A001198 A001199 A001200 * A001202 A001203 A001204

KEYWORD

nonn,nice,hard,more,changed

AUTHOR

N. J. A. Sloane

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .

Last modified December 19 03:55 EST 2014. Contains 252175 sequences.