id:A089367 - OEIS Search Results

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Smallest prime p such that np +1 is a prime, or 0 if no such prime exists.

+0
1

2, 2, 2, 3, 2, 2, 0, 2, 2, 3, 2, 3, 0, 2, 2, 7, 0, 2, 0, 2, 2, 3, 2, 3, 0, 2, 0, 7, 2, 2, 0, 3, 2, 3, 2, 2, 0, 5, 2, 7, 2, 3, 0, 2, 0, 3, 0, 2, 0, 2, 2, 3, 2, 2, 0, 2, 0, 19, 0, 3, 0, 5, 2, 3, 2, 3, 0, 2, 2, 3, 0, 13, 0, 2, 2, 3, 0, 2, 0, 3, 2, 19, 2, 5, 0, 2, 0, 7, 2, 2, 0, 3, 0, 3, 2, 2, 0, 2, 2, 7, 0, 3, 0, 3 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`a(2n+1) = 0 if 4n+3 is composite. Conjecture: There are no other zeros.`
	MAPLE	`for n from 1 to 245 do if(n mod 2 =1 and not isprime(2n+1)) then a[n]:=0: else i:=1:while(not isprime(nithprime(i)+1)) do i:=i+1:od: a[n]:=ithprime(i):fi:od:seq(a[j], j=1..245); (Sascha Kurz)`
	CROSSREFS	`Sequence in context: A116987 A159800 A071137 this_sequence A130192 A104564 A160764` `Adjacent sequences: A089364 A089365 A089366 this_sequence A089368 A089369 A089370`
	KEYWORD	`nonn`
	AUTHOR	`Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Nov 08 2003`
	EXTENSIONS	`More terms from Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), May 09 2004`

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Last modified December 20 00:58 EST 2009. Contains 171054 sequences.

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