1,3

Also numbers n such that (4*10^n+23)/9 is prime.

Index entries for primes involving repunits

Do[ If[ PrimeQ[ 4(10^n - 1)/9 + 3], Print[n]], {n, 5000}]

Sequence in context: A011963 A083844 A026554 this_sequence A127392 A004647 A167030

Adjacent sequences: A099410 A099411 A099412 this_sequence A099414 A099415 A099416

nonn

Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 14 2004