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%I #18 Feb 03 2020 03:14:11
%S 1,1,1,1,2,80,11084874829
%N Number of nonisomorphic Steiner triple systems (STS's) S(2,3,v) on v = 6n+1 or 6n+3 points.
%D L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 304.
%D CRC Handbook of Combinatorial Designs, 1996, p. 70.
%H Petteri Kaski and Patric R. J. Östergård, <a href="http://www.tcs.hut.fi/~pkaski/sts19.ps">The Steiner triple systems of order 19</a>
%H Petteri Kaski and Patric R. J. Östergård, <a href="https://doi.org/10.1090/S0025-5718-04-01626-6">The Steiner triple systems of order 19</a>, Mathematics of Computation, Vol. 73, No. 248 (Oct., 2004), pp. 2075-2092.
%H <a href="/index/St#Steiner">Index entries for sequences related to Steiner systems</a>
%e There are 2 nonisomorphic STS's on 13 points.
%Y Indexed by A047241. Cf. A001201, A030128, A030129, A051390, A124118, A124119.
%K nonn,nice,hard
%O 1,5
%A _N. J. A. Sloane_
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