1,1

Also numbers n such that (5*10^n+31)/9 is prime.

Index entries for primes involving repunits

Do[ If[ PrimeQ[ 5(10^n - 1)/9 + 4], Print[n]], {n, 0, 5000}]

Sequence in context: A090772 A057265 A046525 this_sequence A108987 A035405 A111058

Adjacent sequences: A099415 A099416 A099417 this_sequence A099419 A099420 A099421

nonn

Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 14 2004