OFFSET
0,1
LINKS
J. Brillhart et al., Factorizations of b^n +- 1, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.
FORMULA
a(n) = A002587(2*n). - Amiram Eldar, Feb 01 2020
EXAMPLE
4^3 + 1 = 65 = 5*13, so a(3) = 13.
MATHEMATICA
Table[FactorInteger[4^n + 1][[-1, 1]], {n, 0, 30}]
PROG
(Magma) [Maximum(PrimeDivisors(4^n+1)): n in [0..35]];
(PARI) a(n)=my(f=factor(4^n+1)[, 1]); f[#f] \\ Charles R Greathouse IV, Jul 12 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Vincenzo Librandi, Jul 11 2016
EXTENSIONS
Terms to a(100) in b-file from Vincenzo Librandi, Jul 12 2016
a(101)-a(531) in b-file from Amiram Eldar, Feb 01 2020
a(532)-a(561) in b-file from Max Alekseyev, Apr 25 2022, Apr 15 2023
STATUS
approved