A306751 Numbers k such that 9*10^(2*k) + 3*10^k + 1 is prime.

0, 5, 14, 77, 104, 2603, 2657, 24029

Offset: 1

Author

Seiichi Manyama, Aug 15 2019

Keywords

• nonn
• base
• more

Examples

			         13 is prime ==> a(1) = 0.
        931 = 7^2 * 19.
      90301 = 73 * 1237.
    9003001 = 7 * 757 * 1699.
  900030001 = 13 * 4969 * 13933.
90000300001 is prime ==> a(2) = 5.
		

Crossrefs

Cf. A309738, A309743.

Programs

PARI

for(k=0, 1e3, if(ispseudoprime(9*100^k+3*10^k+1), print1(k", ")))

Extensions

a(8) from Michael S. Branicky, Sep 05 2024