1,2

Also numbers n such that (7*10^(n+1)+11)/9 is prime.

Index entries for primes involving repunits

Makoto Kamada, Factorizations of 77...779.

Do[ If[ PrimeQ[70*(10^n - 1)/9 + 9], Print[n]], {n, 0, 5000}]

Sequence in context: A095523 A060877 A113688 this_sequence A025312 A024508 A025303

Adjacent sequences: A056690 A056691 A056692 this_sequence A056694 A056695 A056696

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