%I A001691 M4660 N1995
%S A001691 1,9,108,3420,114480,7786800
%N A001691 Number of two-element generating sets in the symmetric group S_n.
%D A001691 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A001691 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A001691 J. Denes, Some combinatorial properties of transformations and their 
               connections with the theory of graphs, J. Combin. Theory, 9 (1970), 
               108-116.
%Y A001691 Cf. A086373.
%Y A001691 Sequence in context: A104224 A099676 A051606 this_sequence A157906 A166846 
               A058421
%Y A001691 Adjacent sequences: A001688 A001689 A001690 this_sequence A001692 A001693 
               A001694
%K A001691 nonn
%O A001691 2,2
%A A001691 N. J. A. Sloane (njas(AT)research.att.com).