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A275378 Number of odd prime factors (with multiplicity) of generalized Fermat number 5^(2^n) + 1. 2
1, 1, 1, 2, 2, 3, 3, 3, 5 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Table of n, a(n) for n=0..8.

factordb.com, Status of 5^(2^n)+1.

FORMULA

a(n) = A001222(A199591(n)) - 1. - Felix Fröhlich, Jul 25 2016

EXAMPLE

b(n) = (5^(2^n) + 1)/2.

Complete Factorizations

b(0) = 3

b(1) = 13

b(2) = 313

b(3) = 17*11489

b(4) = 2593*29423041

b(5) = 641*75068993*241931001601

b(6) = 769*3666499598977*96132956782643741951225664001

b(7) = 257*23653200983830003298459393*P62

b(8) = 1655809*101199664791578113*4563566430220614493697*

       12025702000065183805751513732616276516181800961*P88

MATHEMATICA

Table[PrimeOmega[(5^(2^n) + 1)/2], {n, 0, 6}] (* Michael De Vlieger, Jul 26 2016 *)

PROG

(PARI) a(n) = bigomega(factor((5^(2^n)+1)/2))

CROSSREFS

Cf. A199591, A273946.

Sequence in context: A110869 A110876 A324019 * A300506 A300888 A300944

Adjacent sequences:  A275375 A275376 A275377 * A275379 A275380 A275381

KEYWORD

nonn,hard,more

AUTHOR

Arkadiusz Wesolowski, Jul 25 2016

STATUS

approved

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Last modified January 23 10:36 EST 2020. Contains 331171 sequences. (Running on oeis4.)