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A229850 Number of prime factors congruent to 1 mod 3 that divide the Fermat number 2^(2^n) + 1. 2
0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 3, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,11

COMMENTS

a(n) < A046052(n) because all Fermat numbers greater than 3 are equal to 2 (mod 3).

a(n) = 1 if A046052(n) = 2.

If A046052(n) = 3, then a(n) = 0 or 2.

a(n) <= A228846(n) - n - 1 for n = 0 to 11.

REFERENCES

M. Krizek, F. Luca, L. Somer, 17 Lectures on Fermat Numbers: From Number Theory to Geometry, CMS Books in Mathematics, vol. 9, Springer-Verlag, New York, 2001, pp. 61-63, 65-66.

LINKS

Table of n, a(n) for n=0..11.

Wilfrid Keller, Fermat factoring status

Eric Weisstein's World of Mathematics, Fermat Number

CROSSREFS

Cf. A000215, A002476, A023394, A046052, A229854.

Sequence in context: A036112 A266230 A134884 * A269162 A033909 A292240

Adjacent sequences:  A229847 A229848 A229849 * A229851 A229852 A229853

KEYWORD

nonn,hard,more

AUTHOR

Arkadiusz Wesolowski, Oct 01 2013

STATUS

approved

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Last modified January 26 07:37 EST 2022. Contains 350577 sequences. (Running on oeis4.)