id:A117368 - OEIS Search Results

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a(n) = largest prime less than the smallest prime dividing (2n-1).

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2

2, 3, 5, 2, 7, 11, 2, 13, 17, 2, 19, 3, 2, 23, 29, 2, 3, 31, 2, 37, 41, 2, 43, 5, 2, 47, 3, 2, 53, 59, 2, 3, 61, 2, 67, 71, 2, 5, 73, 2, 79, 3, 2, 83, 5, 2, 3, 89, 2, 97, 101, 2, 103, 107, 2, 109, 3, 2, 5, 7, 2, 3, 113, 2, 127, 5, 2, 131, 137, 2, 7, 3, 2, 139, 149, 2, 3, 151, 2, 5, 157, 2 (list; graph; listen)

	OFFSET	`2,1`
	COMMENT	`Placing a 1 between each term of this sequence gets sequence A117365.`
	EXAMPLE	`a(13)=3 because smallest prime dividing 25 is 5 and largest prime less than 5 is 3.`
	MAPLE	`with(numtheory): a:=proc(n): prevprime(factorset(2*n-1)[1]): end: seq(a(n), n=2..90); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 22 2006`
	CROSSREFS	`Cf. A117365.` `Sequence in context: A084346 A096062 A069227 this_sequence A137826 A021429 A124055` `Adjacent sequences: A117365 A117366 A117367 this_sequence A117369 A117370 A117371`
	KEYWORD	`nonn`
	AUTHOR	`Leroy Quet (qq-quet(AT)mindspring.com), Mar 10 2006`
	EXTENSIONS	`More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 22 2006`

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Last modified November 18 20:14 EST 2008. Contains 147244 sequences.

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