A309741 Numbers k such that 6*10^(2*k) + 6*10^k + 1 is prime.

0, 1, 2, 4, 22, 133, 567, 14739, 25390

Offset: 1

Author

Seiichi Manyama, Aug 15 2019

Keywords

• nonn
• more
• base

Examples

			       13 is prime. ==> a(1) = 0.
      661 is prime. ==> a(2) = 1.
    60601 is prime. ==> a(3) = 2.
  6006001 = 2027 * 2963.
600060001 is prime. ==> a(4) = 4.
		

Crossrefs

Cf. A309739.

Programs

PARI

for(k=0, 1e3, if(ispseudoprime(6*100^k+6*10^k+1), print1(k", ")))

Extensions

a(8)-a(9) from Michael S. Branicky, Sep 03 2024