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

1,4

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

Links

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

Example

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

Crossrefs

A152414, A152090, A152091, A152092, A152094, A152095

Sequence in context: A187556 A198103 A105548 * A094242 A199381 A083649

Adjacent sequences: A153090 A153091 A153092 * A153094 A153095 A153096

Keyword

nonn

Author

Pierre CAMI, Dec 18 2008

Status

approved