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A201364 Numbers k such that A057775(k) is the factor of a Fermat number 2^(2^m) + 1 for some m. 5
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Indices of Fermat factors in A057775.
LINKS
Arkadiusz Wesolowski, Table of n, a(n) for n = 1..57
Wilfrid Keller, Fermat factoring status
Eric Weisstein's World of Mathematics, Fermat Number
MATHEMATICA
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
PROG
(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
CROSSREFS
Sequence in context: A062846 A102824 A324588 * A225318 A308267 A177805
KEYWORD
nonn
AUTHOR
EXTENSIONS
a(44)-a(50) from Arkadiusz Wesolowski, May 26 2023
STATUS
approved

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Last modified March 28 09:04 EDT 2024. Contains 371240 sequences. (Running on oeis4.)