A201460 Least k such that (7^n - k)*7^n + 1 is a prime number.

1, 15, 1, 19, 51, 1, 49, 1, 1, 15, 51, 9, 21, 211, 79, 21, 7, 31, 129, 105, 87, 21, 21, 13, 7, 109, 57, 55, 159, 75, 231, 73, 33, 19, 57, 75, 3, 49, 207, 93, 463, 15, 141, 421, 151, 177, 237, 1, 99, 49, 129, 211, 79, 697, 49, 13, 237, 169, 439, 181, 201, 109, 159, 229, 271, 15, 31, 559, 57, 127, 183, 595, 43, 237, 3, 69, 463, 387, 141

Offset: 1

Author

Michel Lagneau, Dec 01 2011

Keywords

• nonn

Crossrefs

Cf. A191619, A200923, A201131.

Programs

Mathematica

 Table[k = 0; While[!PrimeQ[(7^n - k)*7^n + 1], k++]; k, {n, 85}]