A296053 Numbers k such that (46*10^k + 683)/9 is prime.

1, 2, 11, 17, 35, 56, 91, 187, 199, 224, 625, 655, 665, 959, 1457, 1501, 1970, 4478, 12514, 45820, 68698, 113969, 117902, 182896, 192841

Offset

1,2

Comments

For k > 1, numbers k such that the digit 5 followed by k-2 occurrences of the digit 1 followed by the digits 87 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 51w87.

Example

2 is in this sequence because (46*10^2 + 683)/9 = 587 is prime.
Initial terms and associated primes:
a(1) = 1, 127;
a(2) = 2, 587;
a(3) = 11, 511111111187;
a(4) = 17, 511111111111111187;
a(5) = 35, 511111111111111111111111111111111187; etc.

Mathematica

Select[Range[0, 100000], PrimeQ[(46*10^# + 683)/9] &]

Crossrefs

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

Sequence in context: A118839 A091735 A252657 * A234647 A106949 A236687

Adjacent sequences: A296050 A296051 A296052 * A296054 A296055 A296056

Keyword

nonn,more,hard

Author

Robert Price, Dec 03 2017

Extensions

a(22)-a(25) from Robert Price, Mar 24 2019

Status

approved