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 A092873 Prime factors of the odd terms of A007755. 4

%I #11 Oct 07 2017 07:35:26

%S 3,5,11,17,41,83,137,257,641,1097,17477,65537,140417,557057,2384897,

%T 4227137,35946497,71304257,541073537,2281701377,2336497860617,

%U 600470787982337,2278291849363457,4538923050090497,38280596832649217

%N Prime factors of the odd terms of A007755.

%C Catlin shows that if A007755(n) is odd and composite, then its factors are among the A007755(k), k < n. Note that the five Fermat primes are in this sequence.

%H T. D. Noe, <a href="/A092873/b092873.txt">Table of n, a(n) for n=1..288</a> (odd primes in the first 1000 terms of A007755)

%H P. A. Catlin, <a href="http://www.jstor.org/stable/2316857">Concerning the iterated phi-function</a>, Amer Math. Monthly 77 (1970), pp. 60-61.

%K nonn

%O 1,1

%A _T. D. Noe_, Mar 08 2004

%E More terms from _T. D. Noe_, Aug 03 2005

%E a(21) corrected and comment deleted by _T. D. Noe_, Nov 18 2008

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Last modified February 25 04:28 EST 2024. Contains 370309 sequences. (Running on oeis4.)