A276673 Numbers k such that 94*10^k - 3 is prime.

1, 2, 3, 4, 8, 19, 23, 25, 28, 65, 171, 183, 187, 295, 351, 471, 561, 634, 710, 1726, 3947, 4247, 6009, 11065, 13567, 94493, 147871, 182291

Offset: 1

Author

Robert Price, Nov 16 2016

Keywords

• nonn
• more

Comments

For k > 0, numbers k such that the digits 93 followed by k-1 occurrences of the digit 9 followed by the digit 7 is prime (see Example section).

a(29) > 2*10^5.

Examples

			3 is in this sequence because 94*10^n - 3 = 93997 is prime.
Initial terms and associated primes:
a(1) = 1, 937;
a(2) = 2, 9397;
a(3) = 3, 93997;
a(4) = 4, 939997;
a(5) = 8, 9399999997, etc.
		

Links

• Makoto Kamada, Factorization of near-repdigit-related numbers.
• Makoto Kamada, Search for 939w7.

Crossrefs

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

Programs

Mathematica

Select[Range[0, 100000], PrimeQ[94*10^# - 3] &]

PARI

is(n)=ispseudoprime(94*10^n - 3) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(27)-a(28) from Robert Price, May 03 2020