1,2

Also numbers n such that (5*10^(n+1)+31)/9 is prime.

Index entries for primes involving repunits

Makoto Kamada, Factorizations of 55...559.

Do[ If[ PrimeQ[50*(10^n - 1)/9 + 9], Print[n]], {n, 0, 5000}]

Sequence in context: A088176 A046132 A162337 this_sequence A088981 A021014 A021013

Adjacent sequences: A056684 A056685 A056686 this_sequence A056688 A056689 A056690

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