You must set cache to 0. Now you have 16+19 WU in progress. So if any of those WU is prime, you will become double checker, not initial discoverer, since somebody will return result before you: so you will only confirm it is prime.
So set cache to 0, and enjoy
92*10^1439761-1 NEAR-REPDIGIT PRIME :) :) :)
4 * 650^498101-1 CRUS PRIME
314187728^131072+1 GENERALIZED FERMAT
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