What can be said about the set of primes $p$ for which it is proven that an infinite group with all non-trivial proper subgroups cyclic of order $p$ doesn't exist? Specifically, what is the largest such $p$ (say $p\_0$)? All I could find in the literature is $p\_0\le 10^{75}$, but I admit I didn't look very far...



Tarski monster groups: for which primes they don't exist?
The largest known prime for which existence of Tarski monster is not known is $997$, see Adyan, S. I.; Lysënok, I. G. Groups, all of whose proper subgroups are finite cyclic. Izv. Akad. Nauk SSSR Ser. Mat. 55 (1991), no. 5, 933--990; translation in Math. USSR-Izv. 39 (1992), no. 2, 905–957. There are currently no methods of proving that for a given prime $p$ a Tarski monster does not exist except for showing that all finitely generated groups of exponent $p$ are finite. This gives hope that the bound $997$ can be lowered to $665$ (or below $300$ assuming the recent Adian's announcement is correct). 


