A152593 Least k(n) such that 6*k(n)*2^p(n)*(2^p(n)-1)-1 or 6*k(n)*2^p(n)*(2^p(n)-1)+1 (or both) is prime, where p(i)=i-th prime

1, 1, 1, 2, 2, 4, 1, 7, 16, 5, 1, 44, 5, 1, 3, 14, 2, 11, 52, 2, 5, 6, 8, 26, 63, 30, 23, 40, 5, 19, 2, 14, 19, 16, 44, 47, 4, 18, 28, 86, 43, 109, 71, 106, 41, 142, 6, 8, 5, 100, 42, 103, 11, 56, 151, 62, 44, 90, 6, 49, 58, 31, 25, 92, 26, 66, 14, 29, 49, 119, 96, 127, 16, 70, 117

Offset

1,4

Comments

As n increases sum k(n) for i=1 to n / sum p(n) for i=1 to n tends to log(2)/3 for the first 700 primes 0<k(n)<2*p(n)*log(2)

Links

Pierre CAMI, Table of n, a(n) for n=1..700

Example

6*1*2^2*(2^2-1)-1=71 prime as 73 so k(1)=1 6*1*2^3*(2^3-1)+1=337 prime so k(2)=1 6*1*2^5*(2^5-1)+1=5953 prime so k(3)=1

Crossrefs

Sequence in context: A204595 A338823 A173897 * A243548 A105478 A114427

Adjacent sequences: A152590 A152591 A152592 * A152594 A152595 A152596

Keyword

nonn

Author

Pierre CAMI, Dec 09 2008

Status

approved