A273726 Numbers k such that (25*10^k + 59)/3 is prime.

1, 2, 3, 5, 7, 26, 52, 75, 97, 98, 160, 227, 295, 413, 686, 901, 975, 1088, 1481, 2555, 4001, 4361, 5637, 7568, 8641, 19526, 26633, 92186

Offset: 1

Author

Robert Price, May 28 2016

Keywords

• nonn
• more

Comments

For k > 1, numbers k such that the digit 8 followed by k-2 occurrences of the digit 3 followed by the digits 53 is prime (see Example section).

a(29) > 2*10^5.

Examples

			3 is in this sequence because (25*10^3+59)/3 = 8353 is prime.
Initial terms and associated primes:
a(1) = 1, 103;
a(2) = 2, 853;
a(3) = 3, 8353;
a(4) = 5, 833353;
a(5) = 6, 83333353, etc.
		

Links

• Makoto Kamada, Factorization of near-repdigit-related numbers.
• Makoto Kamada, Search for 83w53.

Crossrefs

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

Programs

Mathematica

Select[Range[0, 100000], PrimeQ[(25*10^# + 59)/3] &]

PARI

is(n)=ispseudoprime((25*10^n + 59)/3) \\ Charles R Greathouse IV, Jun 08 2016