1,2

Also numbers n such that (10^n+11)/3 is prime.

a(21) > 10^5. - Robert Price, Nov 02 2014

Table of n, a(n) for n=1..20.

Index entries for primes involving repunits

Do[ If[ PrimeQ[ 3(10^n - 1)/9 + 4], Print[n]], {n, 10000}]

Sequence in context: A127315 A018359 A049383 * A018372 A097350 A062309

Adjacent sequences: A099408 A099409 A099410 * A099412 A099413 A099414

hard,nonn

Robert G. Wilson v, Oct 14 2004

a(16)-a(20) from Robert Price, Nov 02 2014

approved