A135054 Greatest integer K(i)=A085427(n) such that A085427(n)=A085427(n-1)/2 and K(i+1)>K(i) with A085427(n)=least k such that k*2^n-1 is prime ( Mersenne prime when k=1).

1, 7, 13, 15, 17, 75, 102, 173, 181, 229, 513, 539

Offset

1,2

Links

Table of n, a(n) for n=1..12.

Example

A085427 =3,2,1,1,2,1,2,1,5,7,5,3,2,1,5,4,2,1,2,1,14,7,26,13,39,22
A(2)=1,A(1)=2 so A(2)=A(1)/2 so K(1)=1
A(5)=1,A(4)=2 but A(5)=A(2) ..........
A(21)=7,A(20)=14 A(21)=A(20)/2 and A(21)>A(2) so K(2)=7

Crossrefs

Cf. A087425, A135053.

Sequence in context: A328254 A347637 A191976 * A076701 A224773 A349749

Adjacent sequences: A135051 A135052 A135053 * A135055 A135056 A135057

Keyword

nonn,uned

Author

Pierre CAMI, Nov 15 2007

Status

approved