A271505 Numbers k such that (82*10^k + 161)/9 is prime.

1, 2, 4, 5, 7, 8, 14, 17, 22, 49, 130, 136, 142, 170, 196, 220, 967, 1816, 2165, 2542, 2635, 3979, 10319, 11096, 12191, 14381, 14444, 17558, 18230, 42176, 113681

Offset

1,2

Comments

For k > 1, numbers k such that the digit 9 followed by k-2 occurrences of the digit 1 followed by the digits 29 is prime (see Example section).

a(32) > 2*10^5.

Links

Table of n, a(n) for n=1..31.

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

Makoto Kamada, Search for 91w29.

Example

4 is in this sequence because (82*10^4+161)/9 = 91129 is prime.
Initial terms and associated primes:
a(1) = 1, 109;
a(2) = 2, 929;
a(3) = 4, 91129;
a(4) = 5, 911129;
a(5) = 7, 91111129, etc.

Mathematica

Select[Range[0, 100000], PrimeQ[(82*10^# + 161)/9] &]

Prog

(PARI) is(n)=ispseudoprime((82*10^n + 161)/9) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

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

Sequence in context: A082672 A241808 A247865 * A343915 A187054 A135693

Adjacent sequences: A271502 A271503 A271504 * A271506 A271507 A271508

Keyword

nonn,more

Author

Robert Price, Apr 08 2016

Extensions

a(31) from Robert Price, Oct 31 2019

Status

approved