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A092873 Prime factors of the odd terms of A007755. 4
3, 5, 11, 17, 41, 83, 137, 257, 641, 1097, 17477, 65537, 140417, 557057, 2384897, 4227137, 35946497, 71304257, 541073537, 2281701377, 2336497860617, 600470787982337, 2278291849363457, 4538923050090497, 38280596832649217 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

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.

LINKS

T. D. Noe, Table of n, a(n) for n=1..288 (odd primes in the first 1000 terms of A007755)

P. A. Catlin, Concerning the iterated phi-function, Amer Math. Monthly 77 (1970), pp. 60-61.

CROSSREFS

Sequence in context: A129809 A208572 A040176 * A158641 A019386 A283064

Adjacent sequences:  A092870 A092871 A092872 * A092874 A092875 A092876

KEYWORD

nonn

AUTHOR

T. D. Noe, Mar 08 2004

EXTENSIONS

More terms from T. D. Noe, Aug 03 2005

a(21) corrected and comment deleted by T. D. Noe, Nov 18 2008

STATUS

approved

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Last modified May 12 02:23 EDT 2021. Contains 343808 sequences. (Running on oeis4.)