%I #5 Mar 31 2012 13:22:06

%S 1,1,3,1,6,5,5,1,2,2,18,12,12,7,1,1,4,1,9,2,36,10,70,1,3,16,6,3,2,9,

%T 74,4,6,19,20,8,14,2,2,62,3,29,47,11,47,16,58,1,49,18,51,3,12,5,18,23,

%U 1,19,54,7,35,12,7,1,12,3,5,121,70,89,12,61,33,36,9,17,135,35,21,23,20,86,18

%N Least k(n) such that k(n)*5^n*(5^n-1)+j is prime with j= -1 or 1 or both

%C when n increases sum k(n) for i=1 to n / sum n for i=1 to n tends to 13*log(5)/40 when n increases sum k(2*n+1) for i=1 to n / sum (2*n+1) for i=1 to n tends to log(5)/2.5 when n increases sum k(2*n) for i=1 to n / sum (2*n) for i=1 to n tends to log(5)/4

%H Pierre CAMI, <a href="/A153091/b153091.txt">Table of n, a(n) for n = 1..1000</a>

%e 1*5^1*(5^1-1)-1=19 prime so k(1)=1 1*5^2*(5^2-1)-1=599 prime as 601 so k(2)=1

%Y A152414, A152090, A152092, A152093, A152094, A152095

%K nonn

%O 1,3

%A _Pierre CAMI_, Dec 18 2008