A288150 Numbers k such that (25*10^k + 23)/3 is prime.

4, 8, 11, 12, 16, 20, 22, 34, 35, 38, 51, 52, 106, 135, 168, 189, 194, 224, 482, 3456, 4832, 36022, 52119

Offset

1,1

Comments

For k > 1, numbers k such that the digit 8 followed by k-2 occurrences of the digit 3 followed by the digits 41 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 83w41.

Example

4 is in this sequence because (25*10^4 + 23)/3 = 83341 is prime.
Initial terms and associated primes:
a(1) = 4, 83341;
a(2) = 8, 833333341;
a(3) = 11, 833333333341;
a(4) = 12, 8333333333341;
a(5) = 16, 83333333333333341; etc.

Mathematica

Select[Range[0, 100000], PrimeQ[(25*10^# + 23)/3] &]

Crossrefs

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

Sequence in context: A311017 A311018 A098019 * A311019 A068798 A264890

Adjacent sequences: A288147 A288148 A288149 * A288151 A288152 A288153

Keyword

nonn,more,hard

Author

Robert Price, Jun 05 2017

Status

approved