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Search: id:A083519
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| A083519 |
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Beginning with 1, a(i)*a(j) + 2 is prime for all i,j, i != j. |
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+0
1
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| 1, 3, 5, 9, 129, 1179, 21105, 96525, 419925, 13690959, 8403613179
(list; graph; listen)
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OFFSET
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0,2
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EXAMPLE
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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.
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MATHEMATICA
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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 (stefan.steinerberger(AT)gmail.com), Jun 02 2007
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CROSSREFS
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Cf. A083518.
Sequence in context: A123220 A098339 A121622 this_sequence A069193 A078430 A113858
Adjacent sequences: A083516 A083517 A083518 this_sequence A083520 A083521 A083522
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KEYWORD
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hard,more,nonn
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AUTHOR
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Amarnath Murthy and Meenakshi Srikanth (amarnath_murthy(AT)yahoo.com), May 05 2003
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EXTENSIONS
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Corrected and extended by Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Jun 02 2007
a(10) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Nov 11 2008
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