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Least k such that (7^n - k)*7^n + 1 is a prime number.
0

%I #5 Mar 30 2012 18:36:00

%S 1,15,1,19,51,1,49,1,1,15,51,9,21,211,79,21,7,31,129,105,87,21,21,13,

%T 7,109,57,55,159,75,231,73,33,19,57,75,3,49,207,93,463,15,141,421,151,

%U 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

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

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

%Y Cf. A191619, A200923, A201131.

%K nonn

%O 1,2

%A _Michel Lagneau_, Dec 01 2011