id:A123608 - OEIS Search Results

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Numbers n such that n, n+1 and 2n+1 are composite.

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24, 25, 27, 32, 34, 38, 45, 49, 55, 57, 62, 64, 76, 77, 80, 84, 85, 87, 91, 92, 93, 94, 104, 110, 115, 117, 118, 121, 122, 123, 124, 129, 132, 133, 142, 143, 144, 145, 147, 152, 154, 159, 160, 161, 164, 169, 170, 171, 175, 177, 182, 184, 185, 187, 188, 195, 201 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`Also numbers n such that A098735(n) = 1. Also numbers n such that A098077(n) divides n!. Note that n, n+1 and 2n+1 are all primes only for n = 2.`
	MATHEMATICA	`Select[Range[500], !PrimeQ[ # ]&&!PrimeQ[ #+1]&&!PrimeQ[2#+1]&]`
	CROSSREFS	`Cf. A098735, A098077.` `Sequence in context: A004513 A004465 A066024 this_sequence A141587 A027729 A008856` `Adjacent sequences: A123605 A123606 A123607 this_sequence A123609 A123610 A123611`
	KEYWORD	`nonn`
	AUTHOR	`Alexander Adamchuk (alex(AT)kolmogorov.com), Nov 15 2006`

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Last modified November 24 23:16 EST 2009. Contains 167481 sequences.

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