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A201364
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Numbers k such that A057775(k) is the factor of a Fermat number 2^(2^m) + 1 for some m.
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5
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1, 2, 4, 7, 8, 14, 16, 25, 39, 41, 57, 67, 75, 120, 127, 147, 209, 229, 231, 290, 302, 320, 455, 547, 558, 747, 1553, 1947, 2027, 2458, 3313, 3508, 4262, 4727, 6210, 6393, 6539, 6838, 7312, 8242, 8557, 9431, 9450, 12189, 13252, 14254, 14280, 15164, 17909, 18759
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OFFSET
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1,2
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COMMENTS
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Indices of Fermat factors in A057775.
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LINKS
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MATHEMATICA
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lst = {}; Do[k = 1; While[! PrimeQ[p = (2*k - 1)*2^n + 1], k++]; If[IntegerQ[Log[2, MultiplicativeOrder[2, p]]], AppendTo[lst, n]], {n, 320}]; lst
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PROG
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(PARI) isok(n)=my(k=-1, p(k)=k*2^n+1, z(k)=znorder(Mod(2, p(k)))); until(isprime(p(k)), k=k+2); z(k)>>valuation(z(k), 2)==1; \\ Arkadiusz Wesolowski, May 26 2023
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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