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

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

Offset

1,2

Links

Table of n, a(n) for n=1..7.

Example

         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.

Prog

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

Crossrefs

Cf. A309738, A309743.

Sequence in context: A197876 A305017 A007838 * A305341 A316611 A174939

Adjacent sequences: A306748 A306749 A306750 * A306752 A306753 A306754

Keyword

nonn,base,more

Author

Seiichi Manyama, Aug 15 2019

Status

approved