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

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 2*log(6)/9.

Examples

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

Links

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

Crossrefs

Cf. A152414, A152090, A152091, A152093, A152094, A152095.

Programs

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 *)