A229768 Largest prime factor of 2^(2*n+1)+2^(n+1)+1.

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

Author

Colin Barker, Sep 29 2013

Keywords

• nonn

Comments

2^(2*n+1)+2^(n+1)+1 is a factor of 4^(2*n+1)+1.

Examples

			For n=10, 2^(2*n+1)+2^(n+1)+1 = 2099201 = 13*113*1429, so a(10)=1429.
		

Links

• Daniel Suteu, Table of n, a(n) for n = 1..547

Crossrefs

Cf. A085601, A207262, A229747, A229767.

Programs

Mathematica

Table[FactorInteger[2^(2n+1)+2^(n+1)+1][[-1,1]],{n,30}] (* Harvey P. Dale, Nov 03 2017 *)

PARI

a(n) = {f=factor(2^(2*n+1)+2^(n+1)+1); f[matsize(f)[1],1]}