1,2

Numbers n such that 10^n + 8*R_n - 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

Makoto Kamada, Factorizations of 199...997.

Index entries for primes involving repunits.

Do[ If[ PrimeQ[2*10^n - 3], Print[n]], {n, 0, 10000}]

Sequence in context: A117342 A123215 A126129 this_sequence A162222 A010346 A089142

Adjacent sequences: A102944 A102945 A102946 this_sequence A102948 A102949 A102950

more,nonn

Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 16 2004