id:A104278 - OEIS Search Results

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Numbers n such that 2n+1 and 2n-1 are not primes.

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13, 17, 25, 28, 32, 38, 43, 46, 47, 58, 59, 60, 61, 62, 67, 71, 72, 73, 77, 80, 85, 88, 92, 93, 94, 101, 102, 103, 104, 107, 108, 109, 110, 118, 122, 123, 124, 127, 130, 133, 137, 143, 144, 145, 148, 149, 150, 151, 152, 160, 161, 162, 163, 164, 167, 170, 171, 172 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`Complement of A147820. [From Omar E. Pol (info(AT)polprimos.com), Nov 17 2008]`
	EXAMPLE	`a(1)=13 is the first number satisfying simultaneously the two rules.`
	MATHEMATICA	`Select[ Range[300], !PrimeQ[2# + 1] && !PrimeQ[2# - 1] &] (from Robert G. Wilson v (rgwv(AT)rgwv.com), Apr 18 2005)`
	CROSSREFS	`Cf. A040040, A147820.` `Sequence in context: A145483 A125262 A163754 this_sequence A129070 A155923 A052491` `Adjacent sequences: A104275 A104276 A104277 this_sequence A104279 A104280 A104281`
	KEYWORD	`easy,nonn`
	AUTHOR	`Alexandre Wajnberg (alexandre.wajnberg(AT)ulb.ac.be), Apr 17 2005`
	EXTENSIONS	`More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Apr 18 2005`

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Last modified December 8 08:31 EST 2009. Contains 170430 sequences.

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