A201459 Least k such that (7^n - k)*7^n - 1 is a prime number.

1, 1, 5, 7, 7, 11, 5, 29, 13, 29, 5, 1, 77, 1, 13, 101, 65, 77, 175, 29, 77, 121, 49, 23, 41, 31, 613, 101, 13, 37, 127, 47, 197, 31, 107, 97, 275, 17, 619, 47, 7, 199, 85, 31, 47, 17, 97, 253, 17, 37, 5, 103, 215, 119, 335, 257, 277, 121, 313, 89, 157, 187, 25, 7, 571, 11, 197, 53, 13, 101, 49, 199, 67, 389, 109, 13, 25, 41, 337, 647, 77

Offset: 1

Author

Michel Lagneau, Dec 01 2011

Keywords

• nonn

Crossrefs

Cf. A191620, A200922, A201132.

Programs

Mathematica

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