1,2

Also numbers n such that (4*10^(n+1)-31)/9 is prime.

Index entries for primes involving repunits

Do[ If[ PrimeQ[40*(10^n - 1)/9 + 1], Print[n]], {n, 0, 7000}]

Sequence in context: A100001 A110158 A105660 this_sequence A100624 A088809 A069229

Adjacent sequences: A056678 A056679 A056680 this_sequence A056682 A056683 A056684

hard,nonn

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