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A229768
Largest prime factor of 2^(2*n+1)+2^(n+1)+1.
4
13, 41, 29, 109, 2113, 157, 1321, 26317, 525313, 1429, 1657, 268501, 279073, 536903681, 49477, 4327489, 7416361, 231769777, 21841, 43249589, 500177, 29247661, 7484047069, 19707683773, 1326700741, 586477649, 3630105520141, 275415303169, 104399276341
OFFSET
1,1
COMMENTS
2^(2*n+1)+2^(n+1)+1 is a factor of 4^(2*n+1)+1.
LINKS
EXAMPLE
For n=10, 2^(2*n+1)+2^(n+1)+1 = 2099201 = 13*113*1429, so a(10)=1429.
MATHEMATICA
Table[FactorInteger[2^(2n+1)+2^(n+1)+1][[-1, 1]], {n, 30}] (* Harvey P. Dale, Nov 03 2017 *)
PROG
(PARI) a(n) = {f=factor(2^(2*n+1)+2^(n+1)+1); f[matsize(f)[1], 1]}
CROSSREFS
KEYWORD
nonn
AUTHOR
Colin Barker, Sep 29 2013
STATUS
approved