A294570 Numbers k such that (58*10^k + 329)/9 is prime.

0, 1, 3, 6, 19, 22, 27, 48, 70, 130, 364, 594, 603, 799, 2442, 3168, 5059, 5563, 6523, 12282, 13498, 34099, 86242, 122170, 161691

Offset

1,3

Comments

For k > 1, numbers k such that the digit 6 followed by k-2 occurrences of the digit 4 followed by the digits 81 is prime (see Example section).

a(26) > 2*10^5.

Links

Table of n, a(n) for n=1..25.

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

Makoto Kamada, Search for 64w81.

Example

3 is in this sequence because (58*10^3 + 329)/9 = 6481 is prime.
Initial terms and associated primes:
a(1) = 0, 43;
a(2) = 1, 101;
a(3) = 3, 6481;
a(4) = 6, 6444481;
a(5) = 19, 64444444444444444481; etc.

Mathematica

Select[Range[0, 100000], PrimeQ[(58*10^# + 329)/9] &]

Crossrefs

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

Sequence in context: A057268 A085401 A085061 * A306968 A090956 A108972

Adjacent sequences: A294567 A294568 A294569 * A294571 A294572 A294573

Keyword

nonn,more,hard

Author

Robert Price, Nov 02 2017

Extensions

a(24)-a(25) from Robert Price, May 01 2019

Status

approved