A288655 Numbers k such that 10^k - 701 is prime.

7, 13, 22, 28, 29, 49, 53, 70, 124, 151, 287, 394, 400, 946, 979, 1270, 3857, 3944, 5435, 9125, 9589, 49711, 51091, 56849

Offset

1,1

Comments

For k>2, numbers such that k-3 occurrences of the digit 9 followed by the digits 299 is prime (see Example section).

a(25) > 2*10^5.

Links

Table of n, a(n) for n=1..24.

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

Makoto Kamada, Search for 9w299.

Example

7 is in this sequence because 10^7 - 701 = 9999299 is prime.
Initial terms and primes associated:
a(1) = 7, 9999299;
a(2) = 13, 9999999999299;
a(3) = 22, 9999999999999999999299;
a(4) = 28, 9999999999999999999999999299;
a(5) = 29, 99999999999999999999999999299; etc.

Mathematica

Select[Range[3, 100000], PrimeQ[10^# - 701] &]

Crossrefs

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

Sequence in context: A076947 A138077 A353206 * A124192 A335277 A034102

Adjacent sequences: A288652 A288653 A288654 * A288656 A288657 A288658

Keyword

nonn,more,hard

Author

Robert Price, Jun 12 2017

Status

approved