%I A000638 M1244 N0477
%S A000638 1,1,2,4,11,19,56,96,296,554,1593,3094,10723
%N A000638 Number of permutation groups of degree n; also number of conjugacy classes 
               of subgroups of symmetric group S_n; also number of molecular species 
               of degree n.
%D A000638 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A000638 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A000638 F. Bergeron, G. Labelle and P. Leroux, Combinatorial Species and Tree-Like 
               Structures, Camb. 1998, p. 147.
%D A000638 A. C. Lunn and J. K. Senior, Isomerism and Configuration, J. Physical 
               Chem. 33 91929), 1027-1079.
%D A000638 C. C. Sims, Computational methods in the study of permutation groups, 
               pp. 169-183 of J. Leech, editor, Computational Problems in Abstract 
               Algebra. Pergamon, Oxford, 1970.
%D A000638 G. Pfeiffer, Counting Transitive Relations, preprint 2004.
%H A000638 G. Pfeiffer, <a href="http://schmidt.nuigalway.ie/subgroups">Subgroups</
               a>
%H A000638 G. Pfeiffer, <a href="http://www.cs.uwaterloo.ca/journals/JIS/">Counting 
               Transitive Relations</a>, Journal of Integer Sequences, Vol. 7 (2004), 
               Article 04.3.2.
%H A000638 N. J. A. Sloane, <a href="transforms.txt">Transforms</a>
%H A000638 G. Xiao, <a href="http://wims.unice.fr/~wims/en_tool~algebra~permgroup.en.html">
               PermGroup</a>
%F A000638 Euler Transform of A005226. Define b(n), c(n): b(1)=c(0)=0. b(k)=A005227(k), 
               k>1. c(k)=a(k), k>0. A005226(n) is Dirichlet convolution of b and 
               c. - Christian G. Bower, Feb 23 2006
%o A000638 (MAGMA) n := 5; #SubgroupLattice(Sym(n));
%o A000638 (GAP 4r2) Length(ConjugacyClassesSubgroups(SymmetricGroup(n)));
%Y A000638 Cf. A000001, A000019. Unlabeled version of A005432.
%Y A000638 Sequence in context: A018674 A076518 A139785 this_sequence A039824 A076636 
               A011954
%Y A000638 Adjacent sequences: A000635 A000636 A000637 this_sequence A000639 A000640 
               A000641
%K A000638 nonn,hard,nice
%O A000638 0,3
%A A000638 N. J. A. Sloane (njas(AT)research.att.com).
%E A000638 a(11) corrected and a(12) added by Goetz Pfeiffer (goetz.pfeiffer(AT)nuigalway.ie), 
               Jan 21 2004