A135053 Greatest integer M(i)=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).

2, 21, 23, 80, 96, 111, 168, 230, 281, 347, 558, 704

Offset

1,1

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 M(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 M(2)=21

Crossrefs

Cf. A087425, A135054.

Sequence in context: A322925 A294116 A041513 * A042565 A079907 A342727

Adjacent sequences: A135050 A135051 A135052 * A135054 A135055 A135056

Keyword

nonn,uned

Author

Pierre CAMI, Nov 15 2007

Status

approved