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%I #28 Oct 10 2019 04:26:22
%S 1,3,11,49,617,185981
%N Number of nonisomorphic simple matroids of rank 4 on n labeled points.
%H Henry H. Crapo and Gian-Carlo Rota, <a href="/A002773/a002773.pdf">On the foundations of combinatorial theory. II. Combinatorial geometries</a>, Studies in Appl. Math. 49 (1970), 109-133. [Annotated scanned copy of pages 126 and 127 only]
%H Henry H. Crapo and Gian-Carlo Rota, <a href="https://doi.org/10.1002/sapm1970492109">On the foundations of combinatorial theory. II. Combinatorial geometries</a>, Studies in Appl. Math. 49 (1970), 109-133.
%H W. M. B. Dukes, <a href="http://www.stp.dias.ie/~dukes/matroid.html">Tables of matroids</a>.
%H W. M. B. Dukes, <a href="https://web.archive.org/web/20030208144026/http://www.stp.dias.ie/~dukes/phd.html">Counting and Probability in Matroid Theory</a>, Ph.D. Thesis, Trinity College, Dublin, 2000.
%H W. M. B. Dukes, <a href="https://arxiv.org/abs/math/0411557">The number of matroids on a finite set</a>, arXiv:math/0411557 [math.CO], 2004.
%H W. M. B. Dukes, <a href="http://emis.impa.br/EMIS/journals/SLC/wpapers/s51dukes.html">On the number of matroids on a finite set</a>, Séminaire Lotharingien de Combinatoire 51 (2004), Article B51g.
%H Dillon Mayhew and Gordon F. Royle, <a href="https://arxiv.org/abs/math/0702316">Matroids with nine elements</a>, arXiv:math/0702316 [math.CO], 2007. [See Table 2, p. 9.]
%H Dillon Mayhew and Gordon F. Royle, <a href="https://doi.org/10.1016/j.jctb.2007.07.005">Matroids with nine elements</a>, J. Combin. Theory Ser. B 98(2) (2008), 415-431. [See Table 2, p. 420.]
%H Gordon Royle and Dillon Mayhew, <a href="https://web.archive.org/web/20080828102733/http://people.csse.uwa.edu.au/gordon/matroid-integer-sequences.html">9-element matroids</a>.
%H <a href="/index/Mat#matroid">Index entries for sequences related to matroids</a>
%Y Column k=4 of A058730.
%K nonn,nice,more
%O 4,2
%A _N. J. A. Sloane_, Dec 31 2000
%E a(9) from _Petros Hadjicostas_, Oct 09 2019 using the papers by Mayhew and Royle
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