

A005226


Number of atomic species of degree n; also number of connected permutation groups of degree n.
(Formerly M1563)


5



0, 1, 1, 2, 6, 6, 27, 20, 130, 124, 598, 641, 4850, 4772, 35625, 46074, 389839, 487408, 4617554
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OFFSET

0,4


COMMENTS

An atomic species is one that is not the product of smaller species.  Christian G. Bower, Feb 23 2006
A permutation group is connected if it is not the direct product of smaller permutation groups.  Christian G. Bower, Feb 23 2006


REFERENCES

F. Bergeron, G. Labelle and P. Leroux, Combinatorial Species and TreeLike Structures, Camb. 1998, p. 147.
Labelle, Jacques. "Quelques especes sur les ensembles de petite cardinalitĂ©."Ann. Sc. Math. QuĂ©bec 9.1 (1985): 3158.
J. Labelle and Y. N. Yeh, The relation between Burnside rings and combinatorial species, J. Combin. Theory, A 50 (1989), 269284.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS

Table of n, a(n) for n=0..18.
L. Naughton and G. Pfeiffer, Integer sequences realized by the subgroup pattern of the symmetric group, arXiv:1211.1911
N. J. A. Sloane, Transforms


FORMULA

Inverse Euler transform of A000638. Define b(n), c(n), d(): b(1)=d(1)=0. b(k)=A005227(k), k>1. c(k)=A000638(k), k>0. d(k)=a(k), k>1. d is Dirichlet convolution of b and c.  Christian G. Bower, Feb 23 2006


CROSSREFS

Cf. A005227. Unlabeled version of A116655.
Sequence in context: A130865 A282170 A105725 * A087310 A130087 A085087
Adjacent sequences: A005223 A005224 A005225 * A005227 A005228 A005229


KEYWORD

nonn,more,hard


AUTHOR

Simon Plouffe


EXTENSIONS

a(11) corrected and a(12) added by Christian G. Bower, Feb 23 2006 based on Goetz Pfeiffer's edit to A000638.
Could be extended to a(18) now using the new terms for A000637.  N. J. A. Sloane, Jul 30 2010
a(13) from Liam Naughton, Nov 23 2012
a(14)a(18) from the inverse Euler transform of A000637.  R. J. Mathar, Mar 03 2015


STATUS

approved



