A063271 - OEIS

%I #22 May 26 2022 13:16:55

%S 2,41,193,6481,21523361,42521761,769,647753,926510094425921,

%T 282429005041,128653413121,56625998353,24127552321,37644053098601,

%U 36214795668330833,42521761,1716841910146256242328924544641,3833564416504313,56227703611393,278733912072436804273

%N Largest prime factor of 9^(2n)+1 (A063270).

%H Daniel Suteu and Harry J. Smith, <a href="/A063271/b063271.txt">Table of n, a(n) for n = 0..172</a> (terms a(0)..a(50) from Harry J. Smith)

%F a(n) = A006530(A063270(n)) = A002592(2*n) = A074476(4*n). - _Daniel Suteu_, May 26 2022

%t Table[FactorInteger[9^(2n)+1][[-1,1]],{n,0,20}] (* _Harvey P. Dale_, Jan 07 2013 *)

%o (PARI) a(n)={vecmax(factor(9^(2*n) + 1)[,1])} \\ _Harry J. Smith_, Aug 20 2009

%Y Cf. A006530, A063270, A074476, A002592.

%K nonn

%O 0,1

%A _Jason Earls_, Jul 12 2001

%E Definition corrected by _Harry J. Smith_, Aug 20 2009