%I
%S 28,30,44,63,66,70,76,92,102,117,124,130,138,154,170,172,174,182,188,
%T 190,230,236,238,246,266,268,275,279,282,284,286,290,315,316,318,322,
%U 332,354,370,374,387,412,418,426,428,430,434,442,465,470,494,495,498
%N Numbers n such that there are precisely 4 groups of order n.
%H Muniru A Asiru, <a href="/A054396/b054396.txt">Table of n, a(n) for n = 1..369</a>
%H H. U. Besche, B. Eick and E. A. O'Brien, <a href="http://www.icm.tubs.de/ag_algebra/software/small/">The Small Groups Library</a>
%H Gordon Royle, <a href="http://staffhome.ecm.uwa.edu.au/~00013890/remote/cubcay/">Numbers of Small Groups</a>
%H <a href="/index/Gre#groups">Index entries for sequences related to groups</a>
%F Sequence is { k  A000001(k) = 4 }.  _Muniru A Asiru_, Nov 04 2017
%e For n = 28, the 4 groups of order 8 are C7 : C4, C28, D28, C14 x C2 and for n = 30 the 4 groups of order 30 are C5 x S3, C3 x D10, D30, C30 where C, D mean Cyclic, Dihedral groups of the stated order and S is the Symmetric group of the stated degree. The symbols x and : mean direct and semidirect products respectively.  _Muniru A Asiru_, Nov 04 2017
%t Select[Range[500], FiniteGroupCount[#] == 4 &] (* _JeanFrançois Alcover_, Dec 08 2017 *)
%o (GAP) A054396 := Filtered([1..2015], n > NumberSmallGroups(n) = 4); # _Muniru A Asiru_, Nov 04 2017
%Y Cf. A000001, A003277, A054395, A054397, A055561, A054396, A135850.
%K nonn
%O 1,1
%A _N. J. A. Sloane_, May 21 2000
%E More terms from _Christian G. Bower_, May 25 2000
