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

%I #6 Mar 30 2012 18:36:00

%S 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,

%T 87,17,63,45,15,23,9,17,273,51,31,111,277,45,39,51,229,9,109,29,357,

%U 81,1,237,33,137,169,137,847,75,367,57,87,285,25,105,177,113,1

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

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

%Y Cf. A200923, A200923.

%K nonn

%O 1,1

%A _Michel Lagneau_, Nov 27 2011