A295396 Numbers k such that 3*10^k + 11 is prime.

1, 2, 3, 4, 13, 17, 27, 29, 40, 99, 107, 155, 165, 207, 230, 328, 723, 3854, 20929, 65247, 85703, 101065, 186019

Offset

1,2

Comments

For k > 1, numbers such that the digit 3 followed by k-2 occurrences of the digit 0 followed by the digits 11 is prime (see Example section).

a(24) > 2*10^5.

Links

Table of n, a(n) for n=1..23.

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

Makoto Kamada, Search for 30w11

Example

2 is in this sequence because 3*10^2 + 11 = 311 is prime.
Initial terms and primes associated:
a(1) = 1, 41;
a(2) = 2, 311;
a(3) = 3, 3011;
a(4) = 4, 30011;
a(5) = 13, 30000000000011; etc.

Mathematica

Select[Range[0, 100000], PrimeQ[3*10^# + 11] &]

Prog

(PARI) isok(k) = isprime(3*10^k + 11); \\ Michel Marcus, Nov 22 2017

Crossrefs

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

Sequence in context: A126129 A102947 A281512 * A236440 A357954 A162222

Adjacent sequences: A295393 A295394 A295395 * A295397 A295398 A295399

Keyword

nonn,more,hard

Author

Robert Price, Nov 21 2017

Extensions

a(22)-a(23) from Robert Price, Jul 22 2018

Status

approved