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A199423
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Greatest prime factor of n and 2*n+1
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2
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3, 5, 7, 3, 11, 13, 7, 17, 19, 7, 23, 5, 13, 29, 31, 11, 17, 37, 19, 41, 43, 11, 47, 7, 17, 53, 11, 19, 59, 61, 31, 13, 67, 23, 71, 73, 37, 19, 79, 5, 83, 17, 43, 89, 13, 31, 47, 97, 11, 101, 103, 13, 107, 109, 37, 113, 23, 29, 59, 11, 61, 31, 127, 43, 131, 19
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OFFSET
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1,1
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LINKS
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FORMULA
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MATHEMATICA
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Table[Max[Flatten[FactorInteger[{n, 2 n+1}], 1][[All, 1]]], {n, 70}] (* Harvey P. Dale, Mar 25 2020 *)
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PROG
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(PARI) gpf(n)=local(ps); if(n<2, n, ps=factor(n)[, 1]~; ps[#ps])
vector(80, n, gpf(n*(2*n+1)))
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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