1,1

Also numbers n such that (4*10^(n+1)+41)/9 is prime.

Index entries for primes involving repunits

Do[ If[ PrimeQ[40*(10^n - 1)/9 + 9], Print[n]], {n, 5000}]

Sequence in context: A036983 A126666 A154775 this_sequence A066684 A128124 A141062

Adjacent sequences: A056680 A056681 A056682 this_sequence A056684 A056685 A056686

hard,nonn

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