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 A280003 Numbers k such that 7*2^k + 1 is a prime factor of a Fermat number 2^(2^m) + 1 for some m. 3
 14, 120, 290, 320, 95330, 2167800 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 18233956 belongs to this sequence, but its position is currently unknown. - Jeppe Stig Nielsen, Oct 05 2020 LINKS Table of n, a(n) for n=1..6. Proth Search Page, Prime factors of Fermat numbers Eric Weisstein's World of Mathematics, Fermat Number PROG (Magma) IsInteger := func; [n: n in [1..320] | IsPrime(k) and IsInteger(Log(2, Modorder(2, k))) where k is 7*2^n+1]; CROSSREFS Subsequence of A032353. Cf. A000215, A050527, A057778, A201364, A204620, A226366, A280004. Sequence in context: A221230 A240051 A202072 * A004312 A002056 A249980 Adjacent sequences: A280000 A280001 A280002 * A280004 A280005 A280006 KEYWORD nonn,hard,more AUTHOR Arkadiusz Wesolowski, Feb 21 2017 STATUS approved

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Last modified August 14 02:49 EDT 2024. Contains 375146 sequences. (Running on oeis4.)