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A280003 Numbers n such that 7*2^n + 1 is a prime factor of a Fermat number 2^(2^m) + 1 for some m. 2
14, 120, 290, 320, 95330, 2167800 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

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<k | k eq Floor(k)>; [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 September 24 20:13 EDT 2020. Contains 337321 sequences. (Running on oeis4.)