id:A103688 - OEIS Search Results

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a(n)=n if for the least k such that k*n -1 or +1 is prime, k*n -1 and k*n +1 are twin primes or a(n)=0 if only one of k*n -1 and k*n +1 is prime for the least k.

+0
2

1, 2, 3, 4, 6, 0, 0, 9, 0, 0, 12, 0, 0, 15, 0, 0, 18, 0, 0, 21, 0, 23, 0, 25, 0, 0, 0, 0, 30, 0, 0, 0, 0, 0, 36, 0, 0, 0, 0, 0, 42, 0, 0, 0, 46, 47, 0, 0, 50, 51, 0, 0, 0, 0, 0, 0, 0, 0, 60, 0, 0, 0, 0, 0, 0, 0, 0, 69, 0, 0, 72, 0, 0, 75, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 94, 0, 96, 0, 0 (list; graph; listen)

	OFFSET	`1,2`
	EXAMPLE	`For n=5 25-1=9 not prime, 25+1=11 prime so a(5)=0` `For n=6 16-1=5 prime, 16+1=7 prime, 5 and 7 twin primes so a(6)=6`
	CROSSREFS	`Cf. A103689.` `Sequence in context: A062934 A038106 A046942 this_sequence A051703 A004567 A030378` `Adjacent sequences: A103685 A103686 A103687 this_sequence A103689 A103690 A103691`
	KEYWORD	`easy,nonn`
	AUTHOR	`Pierre CAMI (pierrecami(AT)tele2.fr), Feb 12 2005`

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

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