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%I #13 Mar 21 2014 12:10:15
%S 3,2,2,0,4,5,60,3,2,21,28,5,2,199,28,0,234,11,2,3,2,159,10,31,68,145,
%T 0,69,186,163,32,253,26,261,4,0,8,11,62,3,22,43,6,7,8,945,76,7,116,
%U 129,382,93,330,361,2,555,224,1359,78,29,62,39,110,0,1032,37,462,29
%N Smallest k >= 1 such that k^n-n is prime. a(n) = 0 if no such k exists.
%C If n is of the form (pk)^p for some k and some prime p, then a(n) = 0 (See A097764).
%F a(A097764(n)) = 0 for all n.
%e 1^1-1 = 0 is not prime. 2^1-1 = 1 is not prime. 3^1-1 = 2 is prime. Thus, a(1) = 3.
%o (Python)
%o import sympy
%o from sympy import isprime
%o def TwoMin(x):
%o ..for k in range(1,5000):
%o ....if isprime(k**x-x):
%o ......return k
%o x = 1
%o while x < 100:
%o ..print(TwoMin(x))
%o ..x += 1
%Y Cf. A072883, A028870, A153974, A239413, A239414, A239415, A239416, A239417, A239418.
%K nonn
%O 1,1
%A _Derek Orr_, Mar 20 2014
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