A290432 Numbers k such that 9*10^k + 59 is prime.

1, 3, 4, 6, 7, 12, 17, 28, 46, 75, 105, 309, 351, 460, 774, 785, 2206, 5739, 12427, 14501, 17950, 68331, 106559, 166996

Offset

1,2

Comments

For k > 1, numbers such that the digit 9 followed by k-2 occurrences of the digit 0 followed by the digits 59 is prime (see Example section).

a(25) > 2*10^5.

Links

Table of n, a(n) for n=1..24.

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

Makoto Kamada, Search for 90w59,

Example

3 is in this sequence because 9*10^3 + 59 = 9059 is prime.
Initial terms and primes associated:
a(1) = 1, 149;
a(2) = 3, 9059;
a(3) = 4, 90059;
a(4) = 6, 9000059;
a(5) = 7, 90000059; etc.

Mathematica

Select[Range[0, 100000], PrimeQ[9*10^# + 59] &]

Crossrefs

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

Sequence in context: A211384 A281828 A002982 * A276783 A288731 A326422

Adjacent sequences: A290429 A290430 A290431 * A290433 A290434 A290435

Keyword

nonn,more,hard

Author

Robert Price, Oct 06 2017

Extensions

a(23)-a(24) from Robert Price, Jan 13 2020

Status

approved