id:A077654 - OEIS Search Results

Search: id:A077654

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Composite n such that 2n+1 is also composite.

+0
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4, 10, 12, 16, 22, 24, 25, 27, 28, 32, 34, 38, 40, 42, 45, 46, 49, 52, 55, 57, 58, 60, 62, 64, 66, 70, 72, 76, 77, 80, 82, 84, 85, 87, 88, 91, 92, 93, 94, 100, 102, 104, 106, 108, 110, 112, 115, 117, 118, 121, 122, 123, 124, 126, 129, 130 (list; graph; listen)

	OFFSET	`0,1`
	EXAMPLE	`Both 16 and 33 = 16*2+1 are composite, so 16 is in this sequence.`
	PROGRAM	`(PARI) isA077654(n) = !(isprime(n)) & !(isprime(2*n+1)); [From Michael Porter (michael_b_porter(AT)yahoo.com), Oct 01 2009]`
	CROSSREFS	`Cf. A005384, A005385, A067812.` `Sequence in context: A071179 A155475 A023693 this_sequence A095275 A117099 A026180` `Adjacent sequences: A077651 A077652 A077653 this_sequence A077655 A077656 A077657`
	KEYWORD	`nonn`
	AUTHOR	`Lior Manor (lior.manor(AT)gmail.com) Nov 13 2002`

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Last modified November 27 22:38 EST 2009. Contains 167602 sequences.

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