id:A126717 - OEIS Search Results

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Least odd k such that k*2^n-1 is prime.

+0
4

3, 3, 1, 1, 3, 1, 3, 1, 5, 7, 5, 3, 5, 1, 5, 9, 17, 1, 3, 1, 17, 7, 33, 13, 39, 57, 11, 21, 27, 7, 213, 1, 5, 31, 3, 25, 17, 21, 3, 25, 107, 15, 33, 3, 35, 7, 23, 31, 5, 19, 11, 21, 65, 147, 5, 3, 33, 51, 77, 45, 17, 1, 53, 9, 3, 67, 63, 43, 63, 51, 27, 73, 5, 15, 21, 25, 3, 55, 47, 69 (list; graph; listen)

	OFFSET	`0,1`
	LINKS	`T. D. Noe, Table of n, a(n) for n=0..1000` `Yves Gallot's Proth search page`
	EXAMPLE	`a(10)=5 because 52^10-1 is prime but 12^10-1 and 3*2^10-1 are not.`
	MATHEMATICA	`f[n_] := Block[{k = 1}, While[ !PrimeQ[k*2^n - 1], k += 2]; k]; Table[f@n, {n, 0, 80}] - Robert G. Wilson v (rgwv(at)rgwv.com), Feb 20 2007`
	CROSSREFS	`Cf. A035050, A057778, A085427.` `Sequence in context: A098505 A021306 A125300 this_sequence A124039 A096433 A084101` `Adjacent sequences: A126714 A126715 A126716 this_sequence A126718 A126719 A126720`
	KEYWORD	`nonn`
	AUTHOR	`Bernardo Boncompagni (redgolpe(AT)redgolpe.com), Feb 13 2007`
	EXTENSIONS	`More terms from Robert G. Wilson v (rgwv(at)rgwv.com), Feb 20 2007`

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Last modified December 6 22:55 EST 2009. Contains 170429 sequences.

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