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A296444
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Numbers k such that 2*10^(2k) + 2*10^k + 1 are prime.
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3
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0, 2, 3, 6, 10, 276, 746, 1090, 1485, 6186, 8571
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OFFSET
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1,2
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COMMENTS
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Numbers of this form divide 4*10^(4k)+1.
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LINKS
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EXAMPLE
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5, 20201, 2002001, 2000002000001, and 200000000020000000001 are prime, while 221=13*17, 200020001=569*351529, and 20000200001=17*29*1129*35933.
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MATHEMATICA
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ParallelMap[ If[ PrimeQ[2*10^(2 #) + 2*10^# + 1], #, Nothing] &, Range@ 6500] (* Robert G. Wilson v, Dec 13 2017 *)
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PROG
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(PARI) isok(k) = isprime(2*10^(2*k)+2*10^k+1); \\ Michel Marcus, Dec 13 2017
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CROSSREFS
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See A296443 for 2*10^(2k)-2*10^k+1.
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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