Quote:
Originally Posted by devarajkandadai
There seems to be no nonresidues higher than quadratic order;is this related to Fermat's last theorem?

Sorry;just proved that 23 is a nonresidue of 7919 upto infinite order. This was done with aid of my paper "Euler's generalization of Fermat's theorem ( a further generalization) Hawaii international conference ,2004.
Verification : pari code 
Also is(n)=Mod(17,7919)^n==23
select(is,[1..7922]==23