id:A071137 - OEIS Search Results

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Number of times 2n+p is prime, with p=1 or prime p < n.

+0
2

1, 1, 1, 1, 2, 2, 2, 3, 2, 1, 2, 2, 3, 3, 4, 2, 3, 5, 2, 5, 5, 2, 3, 5, 4, 3, 5, 5, 3, 7, 3, 3, 7, 4, 5, 6, 3, 5, 7, 4, 4, 6, 5, 4, 8, 3, 6, 9, 5, 6, 7, 4, 5, 8, 6, 3, 6, 4, 3, 11, 5, 4, 10, 5, 6, 9, 7, 7, 10, 6, 3, 10, 6, 5, 12, 7, 6, 11, 5, 9, 12, 5, 7, 12, 8, 6, 10, 6, 7, 14, 7, 6, 11, 8, 9, 12, 7, 9 (list; graph; listen)

	OFFSET	`1,5`
	EXAMPLE	`a(11)=2 because 22+1 and 22+7 are primes.`
	MATHEMATICA	`For[lst={}; n=1, n<=100, n++, If[PrimeQ[2n+1], cnt=1, cnt=0]; k=1; While[Prime[k]<n, If[PrimeQ[2n+Prime[k]], cnt++ ]; k++ ]; AppendTo[lst, cnt]]; lst`
	CROSSREFS	`Cf. A071127.` `Sequence in context: A135151 A014843 A116987 this_sequence A089367 A130192 A104564` `Adjacent sequences: A071134 A071135 A071136 this_sequence A071138 A071139 A071140`
	KEYWORD	`easy,nonn`
	AUTHOR	`T. D. Noe (noe(AT)sspectra.com), May 28 2002`

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Last modified August 19 23:53 EDT 2008. Contains 142930 sequences.

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