A275802 Numbers k such that (76*10^k + 167)/9 is prime.

1, 2, 4, 5, 7, 10, 16, 19, 28, 37, 41, 44, 53, 311, 490, 1252, 4360, 4732, 5575, 6833, 8878, 11171, 11396, 13079, 14903, 76615

Offset: 1

Author

Robert Price, Aug 09 2016

Keywords

• nonn
• more

Comments

For k > 1, numbers k such that the digit 8 followed by k-2 occurrences of the digit 4 followed by the digits 63 is prime (see Example section).

a(27) > 10^5.

Examples

			4 is in this sequence because (76*10^4+167)/9 = 84463 is prime.
Initial terms and associated primes:
a(1) = 1, 103;
a(2) = 2, 863;
a(3) = 4, 84463;
a(4) = 5, 844463;
a(5) = 7, 84444463, etc.
		

Links

• Makoto Kamada, Factorization of near-repdigit-related numbers.
• Makoto Kamada, Search for 84w63.

Crossrefs

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

Programs

Mathematica

Select[Range[0, 100000], PrimeQ[(76*10^#+167)/9] &]

PARI

is(n)=ispseudoprime((76*10^n+167)/9) \\ Charles R Greathouse IV, Jun 13 2017