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A153091
Least k(n) such that k(n)*5^n*(5^n-1)+j is prime with j= -1 or 1 or both
2
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, 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, 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
OFFSET
1,3
COMMENTS
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
EXAMPLE
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
KEYWORD
nonn
AUTHOR
Pierre CAMI, Dec 18 2008
STATUS
approved