A297417 Numbers k such that (14*10^k + 37)/3 is prime.

0, 1, 2, 3, 4, 6, 8, 10, 14, 36, 41, 213, 229, 555, 569, 2295, 3108, 5944, 7370, 17615, 45894, 141853, 154773, 184150

Offset

1,3

Comments

For k > 1, numbers such that the digit 4 followed by k-2 occurrences of the digit 6 followed by the digits 79 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 46w79

Example

2 is in this sequence because (14*10^2 + 37)/3 = 479 is prime.
Initial terms and primes associated:
a(1) = 0, 17;
a(2) = 1, 59;
a(3) = 2, 479;
a(4) = 3, 4679;
a(5) = 4, 46679; etc.

Mathematica

Select[Range[0, 100000], PrimeQ[(14*10^# + 37)/3] &]

Prog

(PARI) isok(k) = isprime((14*10^k + 37)/3); \\ Michel Marcus, Dec 30 2017

Crossrefs

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

Sequence in context: A045476 A368381 A323360 * A343502 A238876 A211856

Adjacent sequences: A297414 A297415 A297416 * A297418 A297419 A297420

Keyword

nonn,more,hard

Author

Robert Price, Dec 29 2017

Extensions

a(22)-a(24) from Robert Price, Dec 05 2018

Status

approved