A290877 Numbers k such that 3*10^k + 59 is prime.

1, 2, 4, 7, 18, 19, 22, 26, 36, 46, 49, 64, 82, 121, 1204, 1716, 2359, 4541, 7194, 8095, 14857, 18596, 27648, 37066, 109861, 171391

Offset

1,2

Comments

For k > 1, numbers k such that the digit 3 followed by k-2 occurrences of the digit 0 followed by the digits 59 is prime (see Example section).

a(27) > 2*10^5.

Links

Table of n, a(n) for n=1..26.

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

Makoto Kamada, Search for 30w59.

Example

4 is in this sequence because 3*10^4 + 59 = 30059 is prime.
Initial terms and associated primes:
a(1) = 1, 89;
a(2) = 2, 359;
a(3) = 4, 30059;
a(4) = 7; 30000059;
a(5) = 18, 3000000000000000059; etc.

Mathematica

Select[Range[0, 100000], PrimeQ[3*10^# + 59] &]

Prog

(PARI) isok(k) = ispseudoprime(3*10^k + 59) \\ Altug Alkan, Aug 13 2017

Crossrefs

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

Sequence in context: A342538 A076894 A047871 * A103032 A215649 A259351

Adjacent sequences: A290874 A290875 A290876 * A290878 A290879 A290880

Keyword

nonn,more,hard

Author

Robert Price, Aug 13 2017

Extensions

a(25)-a(26) from Robert Price, Aug 25 2018

Status

approved