A153092 Least k(n) such that k(n)*6^n*(6^n-1)+j is prime with j= -1 or 1 or both

1, 1, 1, 1, 3, 2, 3, 2, 20, 4, 5, 2, 9, 2, 27, 7, 12, 3, 3, 2, 3, 6, 6, 1, 18, 8, 2, 17, 2, 14, 55, 1, 18, 4, 59, 18, 30, 26, 32, 3, 14, 59, 42, 35, 40, 22, 7, 17, 26, 6, 28, 3, 15, 11, 6, 32, 30, 18, 14, 4, 85, 3, 1, 65, 13, 64, 7, 18, 40, 8, 68, 5, 5, 6, 107, 7, 88, 25, 6, 3, 1, 21, 8, 12, 9

Offset

1,5

Comments

When n increases sum k(n) for i=1 to n / sum n for i=1 to n tends to log(6)/4.5

Links

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

Example

1*6^1*(6^1-1)-1=29 prime as 31 so k(1)=1

Mathematica

lkn[n_]:=Module[{c=6^n (6^n-1), k=1}, While[NoneTrue[k*c+{1, -1}, PrimeQ], k++]; k]; Array[lkn, 90] (* Harvey P. Dale, Feb 29 2024 *)

Crossrefs

A152414, A152090, A152091, A152093, A152094, A152095

Sequence in context: A362688 A214254 A370903 * A165601 A324030 A275821

Adjacent sequences: A153089 A153090 A153091 * A153093 A153094 A153095

Keyword

nonn

Author

Pierre CAMI, Dec 18 2008

Status

approved