A153093 Least k(n) such that k(n)*7^n*(7^n-1)+j is prime with j= -1 or 1 or both.

1, 1, 1, 2, 9, 1, 2, 1, 1, 5, 13, 1, 6, 1, 6, 14, 4, 4, 7, 5, 6, 5, 12, 3, 6, 3, 9, 3, 20, 9, 14, 7, 43, 22, 5, 11, 4, 4, 48, 14, 8, 56, 36, 7, 83, 47, 47, 1, 2, 74, 15, 12, 22, 15, 17, 47, 20, 20, 5, 8, 12, 26, 6, 26, 55, 16, 32, 45, 24, 46, 19, 58, 6, 29, 19, 26, 83, 45, 17, 48, 6, 16, 152

Offset: 1

Author

Pierre CAMI, Dec 18 2008

Keywords

• nonn

Comments

When n increases sum k(n) for i=1 to n / sum n for i=1 to n tends to log(7)/3.7.

Examples

			1*7^1*(7^1-1)-1=41 prime as 43 so k(1)=1.
		

Links

• Pierre CAMI, Table of n, a(n) for n = 1..1000

Crossrefs

A152414, A152090, A152091, A152092, A152094, A152095.