A294526 Numbers k such that (58*10^k + 419)/9 is prime.

0, 2, 3, 5, 6, 11, 15, 36, 38, 339, 608, 699, 1554, 3984, 4281, 7599, 12461, 13697, 13826, 16431, 39108, 43239, 46685, 103046

Offset

1,2

Comments

For k>1, numbers such that the digit 6 followed by k-2 occurrences of the digit 4 followed by the digits 91 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 64w91.

Example

2 is in this sequence because (58*10^2 + 419)/9 = 691 is prime.
Initial terms and primes associated:
a(1) = 0, 53;
a(2) = 2, 691;
a(3) = 3, 6491;
a(4) = 5, 644491;
a(5) = 6, 6444491; etc.

Mathematica

Select[Range[0, 100000], PrimeQ[(58*10^# + 419)/9] &]

Crossrefs

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

Sequence in context: A180336 A034407 A280218 * A068441 A268935 A112598

Adjacent sequences: A294523 A294524 A294525 * A294527 A294528 A294529

Keyword

nonn,more,hard

Author

Robert Price, Nov 05 2017

Extensions

a(24) from Robert Price, May 18 2019

Status

approved