A275523 Numbers k such that 2*10^k + 93 is prime.

1, 2, 6, 7, 8, 11, 42, 73, 115, 131, 163, 178, 247, 320, 343, 346, 736, 1230, 1556, 3746, 5946, 6020, 6566, 6770, 11302, 14024, 29062, 33268, 37424, 42187, 49216, 51000, 79242, 81287

Offset: 1

Author

Robert Price, Jul 31 2016

Keywords

• nonn
• more

Comments

For k > 1, numbers k such that the digit 2 followed by k-2 occurrences of the digit 0 followed by the digits 93 is prime (see Example section).

a(35) > 10^5.

Examples

			6 is in this sequence because 2*10^6 + 93 = 2000093 is prime.
Initial terms and associated primes:
a(1) = 1, 113;
a(2) = 2, 293;
a(3) = 6, 2000093;
a(4) = 7, 20000093;
a(5) = 8, 200000093, etc.
		

Links

• Makoto Kamada, Factorization of near-repdigit-related numbers.
• Makoto Kamada, Search for 20w93.

Crossrefs

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Programs

Mathematica

Select[Range[0, 100000], PrimeQ[2*10^# + 93] &]

PARI

is(n)=ispseudoprime(2*10^n+93) \\ Charles R Greathouse IV, Jun 13 2017