A302097 Number of odd prime factors (with multiplicity) of generalized Fermat number 13^(2^n) + 1.

1, 2, 1, 1, 3, 4, 4, 3

Offset

0,2

Comments

a(8) >= 6. - Chai Wah Wu, Dec 09 2019

Links

Table of n, a(n) for n=0..7.

factordb.com query on (13^256+1)/2.

Example

b(n) = (13^(2^n) + 1)/2.
Complete factorizations:
b(0) = 7
b(1) = 5*17
b(2) = 14281
b(3) = 407865361
b(4) = 2657*441281*283763713
b(5) = 193*1601*10433*68675120456139881482562689
b(6) = 257*3230593*36713826768408543617*3215877717636198473712500018174097551256193
b(7) = 96769*2940673*P131

Prog

(PARI) a(n) = bigomega((13^(2^n)+1)/2)

Crossrefs

Cf. A275377, A275378, A275379, A275380, A275381, A275382, A275383, A302098.

Sequence in context: A100529 A262953 A226209 * A307277 A210691 A262175

Adjacent sequences: A302094 A302095 A302096 * A302098 A302099 A302100

Keyword

nonn,hard,more

Author

Jeppe Stig Nielsen, Apr 01 2018

Status

approved