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
LINKS
Pierre CAMI, Table of n, a(n) for n = 1..1000
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
CROSSREFS
KEYWORD
nonn
AUTHOR
Pierre CAMI, Dec 18 2008
STATUS
approved