%I A001200 M0726 N0271
%S A001200 1,1,1,2,3,5,10,24,69,384,5250,232929,28872973
%N A001200 Number of linear geometries on n (unlabeled) points.
%C A001200 For the labeled case see A056642.
%C A001200 Also a(n) = 1 + number of non-isomorphic simple rank-3 matroids on n 
               elements (see A058731); a(n) = number of non-isomorphic 2-partitions 
               of a set of size n. For 1-partitions see A000041.
%D A001200 Blackburn et al., A catalogue of combinatorial geometries, Math. Comp 
               27 1973 155-166.
%D A001200 L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 303, #42.
%D A001200 CRC Handbook of Combinatorial Designs, 1996, pp. 216, 697.
%D A001200 J. Doyen, Sur le nombre d'espaces lineaires non isomorphes de n points. 
               Bull. Soc. Math. Belg. 19 1967 421-437.
%D A001200 D. G. Glynn, Rings of geometries II, J. Combin. Theory, A 49 (1988), 
               26-66.
%D A001200 D. G. Glynn, A geometrical isomorphism algorithm, Bull. ICA 7 (1993), 
               36-38.
%D A001200 Ch. Pietsch, On the classification of linear spaces of order 11, J. Comb. 
               Designs, 3 (1995), 185-193.
%D A001200 P. Robillard, On the weighted finite linear spaces. Bull. Soc. Math. 
               Belg. 22 (1970), 227-241.
%D A001200 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A001200 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%H A001200 A. Betten and D. Betten, <a href="http://www.mathe2.uni-bayreuth.de/betten/
               PUB/pub_lin12.html">Linear spaces with at most 12 points</a>, J. 
               Combinatorial Designs, Volume 7, 1999, pp. 119 - 145.
%Y A001200 Cf. A000041, A056642, A058731.
%Y A001200 Sequence in context: A101163 A155587 A125658 this_sequence A050837 A107578 
               A011827
%Y A001200 Adjacent sequences: A001197 A001198 A001199 this_sequence A001201 A001202 
               A001203
%K A001200 nonn,hard,nice
%O A001200 0,4
%A A001200 N. J. A. Sloane (njas(AT)research.att.com), D.Glynn(AT)math.canterbury.ac.nz