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A179205 The smallest index k such that prime(k) *2^n *( prime(k)*2^n -1)-1 is prime. 2
1, 2, 1, 1, 3, 2, 3, 1, 1, 9, 8, 7, 6, 5, 14, 8, 1, 8, 14, 10, 11, 10, 6, 10, 14, 2, 23, 10, 11, 81, 8, 3, 33, 8, 22, 8, 1, 6, 7, 31, 19, 43, 10, 1, 12, 3, 23, 4, 1, 3, 61 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Let S(n) = sum_{k=1..n} a(k) be the partial sums. Then S(n) ~ c*A000217(n) for large n where c is a constant near 0.435.

LINKS

Pierre CAMI, Table of n, a(n) for n = 1...8000

EXAMPLE

2*2*(2*2-1)-1=11 prime so k(1)=1 as 2=p(1) 2*2^2*(2*2^2-1)-1=55 composite 3*2^2*(3*2^2-1)=131 prime so k(2)=2 as 3=p(2)

CROSSREFS

Sequence in context: A006843 A049456 A117506 * A055089 A060117 A196526

Adjacent sequences:  A179202 A179203 A179204 * A179206 A179207 A179208

KEYWORD

nonn

AUTHOR

Pierre CAMI, Jul 02 2010

STATUS

approved

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Last modified December 8 04:27 EST 2016. Contains 278902 sequences.