A265938 Numbers k such that 6*10^k + 91 is prime.

0, 1, 2, 3, 4, 5, 7, 10, 11, 14, 23, 31, 37, 42, 105, 106, 114, 137, 182, 212, 233, 313, 621, 629, 1067, 1570, 4612, 6288, 20030, 21843, 24800, 43694, 179970

Offset: 1

Author

Robert Price, Apr 06 2016

Keywords

• nonn
• more

Comments

For k > 1, numbers k such that the digit 6 followed by k-2 occurrences of the digit 0 followed by the digits 91 is prime (see Example section).

a(34) > 3*10^5.

Examples

			3 is in this sequence because 6*10^3+91 = 6091 is prime.
Initial terms and associated primes:
a(1) = 0, 97;
a(2) = 1, 151;
a(3) = 2, 691;
a(4) = 3, 6091;
a(5) = 4, 60091, etc.
		

Links

• Makoto Kamada, Search for 60w91.

Crossrefs

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

Programs

Mathematica

Select[Range[0, 100000], PrimeQ[6*10^# + 91] &]

PARI

is(n)=ispseudoprime(6*10^n + 91) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(33) from Robert Price, May 21 2019