A152162 - OEIS

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A152162

Least k(n)>=floor(n/2) such that 3*2^k(n)*(2^n-1)-1 or 3*2^k(n)*(2^n-1)+1 is prime (or both primes)

0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 7, 6, 16, 9, 9, 8, 9, 10, 9, 10, 10, 14, 15, 13, 15, 15, 16, 15, 24, 17, 17, 21, 23, 17, 18, 45, 26, 25, 22, 23, 24, 21, 36, 25, 34, 23, 40, 35, 32, 42, 25, 26, 30, 32, 33, 31, 33, 32, 31, 30 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,4`
	COMMENTS	`As n increases (sum k(n) for i=1 to n)/(sum n for i=1 to n) tends to log(2)`
	LINKS	`Pierre CAMI, Table of n, a(n) for n = 1..2000`
	EXAMPLE	`32^0(2^1-1)-1=2 prime so k(1)=0 32^1(2^2-1)-1=17 prime as 19 so k(2)=1 32^1(2^3-1)-1=41 prime as 43 so k(2)=1`
	CROSSREFS	`Sequence in context: A029027 A035448 A060969 * A030699 A083802 A100881` `Adjacent sequences: A152159 A152160 A152161 * A152163 A152164 A152165`
	KEYWORD	`nonn`
	AUTHOR	`Pierre CAMI (pierre-cami(AT)bbox.fr), Nov 27 2008`

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Last modified February 16 12:15 EST 2012. Contains 205909 sequences.