A293276 Numbers k such that (74*10^k + 133)/9 is prime.

0, 1, 3, 4, 7, 10, 19, 24, 27, 85, 93, 99, 133, 292, 309, 676, 894, 2076, 2236, 10968, 20628, 29521, 49054, 57763, 139723, 150616

Offset

1,3

Comments

For k > 1, numbers k such that the digit 8 followed by k-2 occurrences of the digit 2 followed by the digits 37 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 82w37.

Example

3 is in this sequence because (74*10^3 + 133)/9 = 8237 is prime.
Initial terms and associated primes:
a(1) = 0, 23;
a(2) = 1, 97;
a(3) = 3, 8237;
a(4) = 4, 82237;
a(5) = 7, 82222237; etc.

Mathematica

Select[Range[0, 100000], PrimeQ[(74*10^# + 133)/9] &]

Crossrefs

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

Sequence in context: A143607 A193826 A032715 * A291609 A291870 A002887

Adjacent sequences: A293273 A293274 A293275 * A293277 A293278 A293279

Keyword

nonn,more,hard

Author

Robert Price, Oct 04 2017

Extensions

a(25)-a(26) from Robert Price, Jun 21 2019

Status

approved