29 Jan
2012
29 Jan
'12
1:21 p.m.
David Wilson:
I realized that this sequence would be a(n) = smallest prime >= 10^n with primitive root 10.
The primitive-root-10 (A001913) criterion assures us a large decimal expansion period from which to cull our n-digit collection. That is also shared by primitive-root-10 primes < 10^n. How do you know one of these doesn't eventually luck into a 9*10^(n-1) distinct n-digit count?