OFFSET
1,1
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) = A005420(3*n). - Robert Israel, Jul 12 2016
EXAMPLE
8^5 -1 = 32767 = 7*31*151, so a(5) = 151.
MAPLE
f:= n -> max(map(t -> max(numtheory:-factorset(subs(x=2, t[1]))), factors(x^(3*n)-1)[2])):
map(f, [$1..120]); # Robert Israel, Jul 12 2016
MATHEMATICA
Table[FactorInteger[8^n - 1][[-1, 1]], {n, 40}]
PROG
(Magma) [Maximum(PrimeDivisors(8^n-1)): n in [1..40]];
CROSSREFS
KEYWORD
nonn
AUTHOR
Vincenzo Librandi, Jul 11 2016
EXTENSIONS
Terms to a(100) in b-file from Vincenzo Librandi, Jul 13 2016
a(101)-a(402) in b-file from Amiram Eldar, Feb 02 2020
a(403)-a(500) in b-file from Max Alekseyev, Apr 25 2022, Sep 11 2022, Dec 05 2022, Feb 25 2023
STATUS
approved