A063271 Largest prime factor of 9^(2n)+1 (A063270).

2, 41, 193, 6481, 21523361, 42521761, 769, 647753, 926510094425921, 282429005041, 128653413121, 56625998353, 24127552321, 37644053098601, 36214795668330833, 42521761, 1716841910146256242328924544641, 3833564416504313, 56227703611393, 278733912072436804273

Offset

0,1

Links

Daniel Suteu and Harry J. Smith, Table of n, a(n) for n = 0..172 (terms a(0)..a(50) from Harry J. Smith)

Formula

a(n) = A006530(A063270(n)) = A002592(2*n) = A074476(4*n). - Daniel Suteu, May 26 2022

Mathematica

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

Prog

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

Crossrefs

Cf. A006530, A063270, A074476, A002592.

Sequence in context: A090195 A287335 A212837 * A142160 A174615 A109125

Adjacent sequences: A063268 A063269 A063270 * A063272 A063273 A063274

Keyword

nonn

Author

Jason Earls, Jul 12 2001

Extensions

Definition corrected by Harry J. Smith, Aug 20 2009

Status

approved