A285938 Numbers k such that (19*10^k + 149)/3 is prime.

1, 2, 5, 7, 8, 11, 16, 29, 73, 169, 212, 227, 262, 547, 863, 1325, 2035, 4808, 8405, 13612, 16687, 19456, 122501

Offset

1,2

Comments

For k>1, numbers such that the digit 6 followed by k-2 occurrences of the digit 3 followed by the digits 83 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 63w83.

Example

5 is in this sequence because (19*10^5+149)/3 = 633383 is prime.
Initial terms and primes associated:
a(1) = 1, 113;
a(2) = 2, 683;
a(3) = 5, 633383;
a(4) = 7, 63333383;
a(5) = 8, 633333383; etc.

Mathematica

Select[Range[0, 100000], PrimeQ[(19*10^# + 149)/3] &]

Crossrefs

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

Sequence in context: A153308 A370856 A216565 * A325441 A192111 A294635

Adjacent sequences: A285935 A285936 A285937 * A285939 A285940 A285941

Keyword

nonn,more,hard

Author

Robert Price, Apr 29 2017

Extensions

a(23) from Robert Price, May 17 2019

Status

approved