OFFSET
0,2
COMMENTS
a(8) >= 6. - Chai Wah Wu, Dec 09 2019
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
KEYWORD
nonn,hard,more
AUTHOR
Jeppe Stig Nielsen, Apr 01 2018
STATUS
approved