1,2

Also numbers n such that (4*10^n-1)/3 is prime.

Makoto Kamada, Factorizations of 133...33

Index entries for primes involving repunits

Do[ If[ PrimeQ[ 10^n + 3*(10^n-1)/9], Print[n]], {n, 0, 30470}]

Sequence in context: A116042 A103003 A024845 this_sequence A070007 A154267 A051867

Adjacent sequences: A056695 A056696 A056697 this_sequence A056699 A056700 A056701

hard,nonn

Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 10 2000