A122862 Numbers k such that (9*10^k - 11)/7 is prime.

2, 260, 650, 1928, 5768, 36548

Offset: 1

Author

Zak Seidov, Sep 22 2006

Keywords

• nonn
• more

Comments

All terms are of the form 2+6*i, i = 0,1,... .

Are there any k's such that (9*10^k - 11)/p is prime for prime p<>7?

Crossrefs

Cf. A100275.

Programs

Mathematica

Do[If[PrimeQ[(9*10^n-11)/7],Print[n]],{n,2,7220,6}]

PARI

is(n)=ispseudoprime((9*10^n-11)/7) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(6) from Michael S. Branicky, Jul 08 2025