1,1

Also numbers n such that (5*10^n-41)/9 is prime.

Index entries for primes involving repunits

Do[ If[ PrimeQ[ 5(10^n - 1)/9 - 4], Print[n]], {n, 15000}]

Adjacent sequences: A099412 A099413 A099414 this_sequence A099416 A099417 A099418

Sequence in context: A041309 A041310 A066321 this_sequence A042293 A061097 A121288

nonn,bref

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