A277066 Numbers k such that (266*10^k - 11) / 3 is prime.

1, 2, 3, 4, 7, 9, 10, 14, 28, 58, 93, 121, 135, 207, 350, 423, 602, 859, 1026, 1864, 1966, 13738, 23299, 28126, 38691, 39403, 47499, 93577, 124022, 177577

Offset: 1

Author

Robert Price, Sep 27 2016

Keywords

• nonn
• more

Comments

For k > 0, numbers k such that the digits 88 followed by k-1 occurrences of the digit 6 followed by the digit 3 is prime (see Example section).

a(31) > 3*10^5.

Examples

			3 is in this sequence because (266*10^3 - 11) / 3 = 88663 is prime.
Initial terms and associated primes:
a(1) = 1, 883;
a(2) = 2, 8863;
a(3) = 3, 88663;
a(4) = 4, 886663;
a(5) = 7, 886666663, etc.
		

Links

• Makoto Kamada, Factorization of near-repdigit-related numbers.
• Makoto Kamada, Search for 886w3.

Crossrefs

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

Programs

Mathematica

Select[Range[0, 100000], PrimeQ[(266*10^# - 11) / 3] &]

PARI

is(n)=ispseudoprime((266*10^n - 11)/3) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(29)-a(30) from Robert Price, Apr 01 2020