1,2

Also numbers n such that 7*10^n + 9*R_n - 8 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

Makoto Kamada, Factorizations of 799...991.

Index entries for primes involving repunits.

Do[ If[ PrimeQ[8*10^n - 9], Print[n]], {n, 0, 10000}]

Sequence in context: A102175 A139200 A102181 this_sequence A070369 A104215 A093685

Adjacent sequences: A103065 A103066 A103067 this_sequence A103069 A103070 A103071

more,nonn

Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 19 2005