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

1,2

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.

Links

Table of n, a(n) for n=1..28.

Makoto Kamada, Factorization of near-repdigit-related numbers.

Makoto Kamada, Search for 939w7.

Example

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.

Mathematica

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

Prog

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

Crossrefs

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

Sequence in context: A296109 A102276 A215897 * A282815 A339630 A105055

Adjacent sequences: A276670 A276671 A276672 * A276674 A276675 A276676

Keyword

nonn,more

Author

Robert Price, Nov 16 2016

Extensions

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

Status

approved