A272523 Numbers k such that (265*10^k + 17)/3 is prime.

2, 3, 4, 10, 35, 60, 65, 72, 87, 218, 226, 326, 365, 461, 611, 1244, 1566, 4839, 4913, 5396, 7020, 8410, 9714, 10362, 11405, 21695, 25240, 56076, 56588, 74579, 81990, 114736

Offset: 1

Author

Robert Price, May 01 2016

Keywords

• nonn
• more

Comments

For k > 1, numbers k such that the digits 88 followed by k-1 occurrences of the digit 3 followed by the digit 9 is prime (see Example section).

a(33) > 2*10^5.

Examples

			3 is in this sequence because (265*10^3 + 17)/3 = 88339 is prime.
Initial terms and associated primes:
a(1) = 2, 8839;
a(2) = 3, 88339;
a(3) = 4, 883339;
a(4) = 10, 883333333339;
a(5) = 35, 8833333333333333333333333333333333339, etc.
		

Links

• Makoto Kamada, Factorization of near-repdigit-related numbers.
• Makoto Kamada, Search for 883w9.

Crossrefs

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

Programs

Mathematica

Select[Range[0, 100000], PrimeQ[(265*10^# + 17)/3] &]

PARI

is(n)=ispseudoprime((265*10^n + 17)/3) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(32) from Robert Price, Mar 21 2020