A283684 Numbers k such that 3*10^k + 17 is prime.

1, 2, 5, 6, 13, 17, 24, 29, 38, 43, 59, 92, 350, 365, 679, 1016, 2958, 4434, 6306, 8819, 11687, 13484, 22189, 43034, 69354, 78146, 78631, 150182

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 17 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 30w17.

Example

2 is in this sequence because 3*10^2 + 17 = 317 is prime.
Initial terms and associated primes:
a(1) = 1, 47;
a(2) = 2, 317;
a(3) = 5, 300017;
a(4) = 6, 3000017;
a(5) = 13, 30000000000017; etc.

Mathematica

Select[Range[0, 100000], PrimeQ[3*10^# + 17] &]

Prog

(PARI) isok(n) = isprime((3*10^n + 17)); \\ Indranil Ghosh, Mar 14 2017

Crossrefs

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

Sequence in context: A342569 A028259 A327472 * A325285 A323348 A181314

Adjacent sequences: A283681 A283682 A283683 * A283685 A283686 A283687

Keyword

nonn,more,hard

Author

Robert Price, Mar 14 2017

Extensions

a(28) from Robert Price, Jul 27 2018

Status

approved