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A094474
a(n) is the largest prime factor of 2^n + 3^n.
7
5, 13, 7, 97, 11, 61, 463, 401, 577, 4621, 35839, 5521, 4057, 369181, 241, 14177, 7039, 181, 555029, 3121, 92233, 2414250301, 13249, 41432641, 513101, 13761229, 377604937, 3001769, 148466603, 24001, 22674269, 1607133116929, 22270249, 1282861452271981, 392943879511
OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..546 (terms 1..120 from Vincenzo Librandi)
FORMULA
a(n) = A006530(A007689(n)). - Amiram Eldar, Dec 27 2019
EXAMPLE
n = 100, 2^100 + 3^100 = 41 * 97 * 281 * 3121 * 742801 * 20017001 * 9937984196743741414107401 so a(100) = 9937984196743741414107401.
MATHEMATICA
Table[Part[Reverse[Flatten[FactorInteger[2^w + 3^w]]], 2], {w, 1, 100}]
PROG
(Magma) [Max(PrimeFactors(2^n + 3^n)):n in[1..68]]; // Vincenzo Librandi, Dec 25 2019
CROSSREFS
Sequence in context: A340802 A088315 A138296 * A064109 A175484 A210694
KEYWORD
nonn
AUTHOR
Labos Elemer, Jun 01 2004
EXTENSIONS
a(34)-a(35) from Vincenzo Librandi, Dec 25 2019
STATUS
approved