1,5

Sum a(n) for n=1 to k / sum n for n=1 to k tends to 2*log(3)/7.

Pierre CAMI, Table of n, a(n) for n = 1..2000

1*3^1*(3^1-1)-1=5 prime as 7 so k(1)=1 1*3^2*(3^2-1)-1=71 prime as 73 so k(2)=1

Cf. A152414, A152091, A152092, A152093, A152094, A152095.

Sequence in context: A015112 A174690 A156869 * A203002 A073483 A006956

Adjacent sequences: A153087 A153088 A153089 * A153091 A153092 A153093

nonn

Pierre CAMI, Dec 18 2008

approved