1,1

Also numbers n such that (2*10^n+61)/9 is prime.

Index entries for primes involving repunits

Do[ If[ PrimeQ[ 2(10^n - 1)/9 + 7], Print[n]], {n, 5000}]

Adjacent sequences: A099407 A099408 A099409 this_sequence A099411 A099412 A099413

Sequence in context: A039575 A104870 A114411 this_sequence A102033 A072246 A024781

nonn

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