In this article we introduce and study two classes of finite groups for which the orders of their subgroups satisfy a certain inequality. These are closely connected to some well-known arithmetic classes of natural numbers.
"Finite groups determined by an inequality of the orders of their subgroups." Bull. Belg. Math. Soc. Simon Stevin 15 (4) 699 - 704, November 2008. https://doi.org/10.36045/bbms/1225893949