%N The number of groups of order n that are not Lagrangian.
%C A group of order n is Lagrangian if it has a subgroup of order d for each divisor d of n.
%H Mathematics StackExchange Discussion, <a href="http://math.stackexchange.com/questions/2144077/complete-classification-of-the-groups-for-which-converse-of-lagranges-theorem-h">Complete classification of the groups for which converse of Lagrange's Theorem holds</a>
%o local i,N,G,m;
%o for i in [1..N] do
%o if Set(List(ConjugacyClassesSubgroups( G ),t->Size(Representative(t)))<>DivisorsInt(n)
%o then m:=m+1; fi;
%o return m;
%A _W. Edwin Clark_, Feb 20 2017