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A275377 Number of odd prime factors (with multiplicity) of generalized Fermat number 3^(2^n) + 1. 4
0, 1, 1, 2, 1, 1, 1, 5, 4, 6 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

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

Arkadiusz Wesolowski, A 93-digit prime factor of b(9)

FORMULA

a(n) = A001222(A059919(n)) - 1 for n > 0. - Felix Fröhlich, Jul 25 2016

EXAMPLE

b(n) = (3^(2^n) + 1)/2.

Complete Factorizations

b(0) = 2

b(1) = 5

b(2) = 41

b(3) = 17*193

b(4) = 21523361

b(5) = 926510094425921

b(6) = 1716841910146256242328924544641

b(7) = 257*275201*138424618868737*3913786281514524929*P21

b(8) = 12289*8972801*891206124520373602817*P90

b(9) = 134382593*22320686081*12079910333441*100512627347897906177*P93*P101

PROG

(PARI) a001222(n) = bigomega(n)

a059919(n) = 3^(2^n)+1

a(n) = if(n==0, 0, a001222(a059919(n))-1) \\ Felix Fröhlich, Jul 25 2016

CROSSREFS

Cf. A059919, A273945.

Sequence in context: A227578 A181783 A121395 * A219585 A292464 A090628

Adjacent sequences:  A275374 A275375 A275376 * A275378 A275379 A275380

KEYWORD

nonn,hard,more

AUTHOR

Arkadiusz Wesolowski, Jul 25 2016

EXTENSIONS

a(9) was found in 2008 by Tom Womack

STATUS

approved

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Last modified January 28 12:58 EST 2020. Contains 331321 sequences. (Running on oeis4.)