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A275380 Number of odd prime factors (with multiplicity) of generalized Fermat number 7^(2^n) + 1. 2
0, 2, 1, 2, 2, 3, 3, 5, 3, 6 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..9.

FORMULA

a(n) = A001222(A078304(n)) for n > 0. - Felix Fröhlich, Jul 25 2016

EXAMPLE

b(n) = (7^(2^n) + 1)/2.

Complete Factorizations

b(0) = 2*2

b(1) = 5*5

b(2) = 1201

b(3) = 17*169553

b(4) = 353*47072139617

b(5) = 7699649*134818753*531968664833

b(6) = 35969*1110623386241*15266848196793556098085000332888634369

b(7) = 257*769*197231873*6856531741041792239054980342217258517995521*P52

b(8) = 28667393*126575155274810369*P192

b(9) = 13313*943558259713*

       275102002206713516320479233*1338330888777063359811677099009*

       656929861401793262700329631944023570433*P321

CROSSREFS

Cf. A078304, A273948.

Sequence in context: A029172 A240864 A241322 * A161052 A161256 A161281

Adjacent sequences:  A275377 A275378 A275379 * A275381 A275382 A275383

KEYWORD

nonn,hard,more

AUTHOR

Arkadiusz Wesolowski, Jul 25 2016

EXTENSIONS

a(9) was found by Nestor de Araújo Melo and Geoffrey Reynolds (2008)

STATUS

approved

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Last modified January 20 08:07 EST 2020. Contains 331081 sequences. (Running on oeis4.)