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A050566
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Numbers n such that 81*2^n-1 is prime.
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4
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3, 5, 11, 17, 21, 27, 81, 101, 107, 327, 383, 387, 941, 1665, 3515, 4007, 4727, 7137, 16257, 16833, 21243, 24239, 35435, 59925, 91673, 153455, 165341, 183167, 190349, 240743, 253385, 308325, 741917
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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b=81; i=0; Table[While[i++; cp=b*2^i-1; !PrimeQ[cp]]; i, {j, 1, 17}]
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PROG
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CROSSREFS
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KEYWORD
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hard,nonn
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AUTHOR
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EXTENSIONS
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More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
Lei Zhou, Nov 08 2013, added a Mathematica program for small elements.
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STATUS
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approved
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