A201131 Least k such that (5^n - k)*5^n + 1 is a prime number.

3, 1, 11, 1, 5, 19, 9, 1, 11, 15, 9, 69, 27, 21, 77, 85, 53, 1, 5, 201, 9, 43, 93, 403, 45, 87, 17, 63, 45, 15, 23, 9, 17, 273, 51, 31, 111, 277, 45, 39, 51, 229, 9, 109, 29, 357, 81, 1, 237, 33, 137, 169, 137, 847, 75, 367, 57, 87, 285, 25, 105, 177, 113, 1

Offset: 1

Author

Michel Lagneau, Nov 27 2011

Keywords

• nonn

Crossrefs

Cf. A200923, A200923.

Programs

Mathematica

Table[k = 0; While[!PrimeQ[(5^n - k)*5^n + 1], k++]; k, {n, 85}]