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 A083519 Beginning with 1, a(i)*a(j) + 2 is prime for all i,j, i != j. 0
 1, 3, 5, 9, 129, 1179, 21105, 96525, 419925, 13690959, 8403613179 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS EXAMPLE 1*3+2, 3*5+2,1*5 +2, etc. are primes. 9*1+2 = 11, 9*3+2=29, 9*5+2=47 are all prime numbers, therefore we can say that a(4) = 9. MATHEMATICA a = {1}; For[n = 2, n < 1000000, n++, b = Table[a[[i]]*n + 2, {i, 1, Length[ a]}]; If[Union[PrimeQ[b], PrimeQ[b]] == {True}, AppendTo[a, n]]]; a - Stefan Steinerberger, Jun 02 2007 CROSSREFS Cf. A083518. Sequence in context: A098339 A121622 A188983 * A211414 A173706 A176629 Adjacent sequences:  A083516 A083517 A083518 * A083520 A083521 A083522 KEYWORD hard,more,nonn AUTHOR Amarnath Murthy and Meenakshi Srikanth (amarnath_murthy(AT)yahoo.com), May 05 2003 EXTENSIONS Corrected and extended by Stefan Steinerberger, Jun 02 2007 a(10) from Donovan Johnson, Nov 11 2008 STATUS approved

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