1,2

Also numbers n such that 6*10^n + 9*R_n - 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

Makoto Kamada, Factorizations of 699...997.

Index entries for primes involving repunits.

Do[ If[ PrimeQ[7*10^n - 3], Print[n]], {n, 0, 10000}]

Sequence in context: A032408 A018908 A052548 this_sequence A103016 A061032 A091424

Adjacent sequences: A103046 A103047 A103048 this_sequence A103050 A103051 A103052

more,nonn

Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 18 2005