1,2

Also numbers n such that (7*10^(n+1)-61)/9 is prime.

Index entries for primes involving repunits

Makoto Kamada, Factorizations of 77...771.

Do[ If[ PrimeQ[70*(10^n - 1)/9 + 1], Print[n]], {n, 0, 7000}]

Sequence in context: A110932 A112880 A100541 this_sequence A107911 A143800 A003335

Adjacent sequences: A056685 A056686 A056687 this_sequence A056689 A056690 A056691

hard,nonn

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

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008