OFFSET
0,4
LINKS
factordb.com, Status of 5^(2^n)+1.
FORMULA
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
KEYWORD
nonn,hard,more
AUTHOR
Arkadiusz Wesolowski, Jul 25 2016
STATUS
approved