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