A293535 Numbers k such that 2*10^k + 63 is prime.

1, 2, 3, 4, 5, 7, 9, 16, 35, 40, 71, 79, 82, 153, 167, 229, 652, 851, 1034, 1216, 1235, 1300, 7447, 26360, 30553, 36994, 47321, 95095, 141448, 179602

Offset

1,2

Comments

For k>1, numbers such that the digit 2 followed by k-2 occurrences of the digit 0 followed by the digits 63 is prime (see Example section).

a(31) > 2*10^5.

Links

Table of n, a(n) for n=1..30.

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

Makoto Kamada, Search for 20w63

Example

2 is in this sequence because 2*10^2 + 63 = 263 is prime.
Initial terms and primes associated:
a(1) = 1, 83;
a(2) = 2, 263;
a(3) = 3, 2063;
a(4) = 4, 20063;
a(5) = 5, 200063; etc.

Mathematica

Select[Range[0, 100000], PrimeQ[2*10^# + 63] &]

Crossrefs

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

Sequence in context: A050763 A252023 A282895 * A261170 A051453 A357166

Adjacent sequences: A293532 A293533 A293534 * A293536 A293537 A293538

Keyword

nonn,more,hard

Author

Robert Price, Oct 11 2017

Extensions

a(29)-a(30) from Robert Price, May 08 2018

Status

approved