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 A297625 Primes of the form (2^(p^k) - 1)/(2^(p^(k - 1)) - 1), with p prime and k > 1. 0
 5, 17, 73, 257, 65537, 262657, 4432676798593 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primes of the form Phi(x, 2), where x is a proper prime power and Phi is the cyclotomic polynomial. Together with 3, supersequence of A019434. Also called Mersenne-Fermat primes. a(8) has 1031 digits and is too large to include. REFERENCES Fredrick Kennard, Unsolved Problems in Mathematics, Lulu Press, 2015, p. 160. LINKS Wikipedia, Mersenne-Fermat primes PROG (MAGMA) lst:=[]; r:=7; pr:=PrimesUpTo(r); for k in [2..r] do for c in [1..#pr] do p:=pr[c]; if p^k le r^2 then MF:=Truncate((2^(p^k)-1)/(2^(p^(k-1))-1)); if IsPrime(MF) then Append(~lst, MF); end if; end if; end for; end for; Sort(lst); CROSSREFS Cf. A019434, A051156, A140797, A187823, A245730, A246547. Sequence in context: A146577 A211405 A187823 * A084777 A149717 A149718 Adjacent sequences:  A297622 A297623 A297624 * A297626 A297627 A297628 KEYWORD nonn AUTHOR Arkadiusz Wesolowski, Jan 04 2018 STATUS approved

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Last modified December 1 13:22 EST 2021. Contains 349429 sequences. (Running on oeis4.)