A140538 Greatest prime factor of 2*n^4 + 1.

3, 11, 163, 19, 139, 2593, 1601, 2731, 1193, 113, 227, 619, 577, 8537, 73, 43691, 55681, 209953, 307, 9697, 388963, 52057, 1091, 337, 260417, 304651, 3011, 4937, 471521, 1620001, 691, 5419, 32491, 46889, 90947, 25643, 11057, 15619, 7499, 7793

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..2000

Formula

a(n) = A006530(2n^4+1) = A076565(n^4). - R. J. Mathar, Aug 04 2008

Example

a(2)= 11 because 2*2^4+1 = 33 = 3*11, greatest prime factor is 11.

Mathematica

Table[Max[Transpose[FactorInteger[2 n^4 + 1]][[1]]], {n, 50}] (* Vincenzo Librandi, Feb 17 2015 *)

Prog

(PARI) a(n) = f = factor(2*n^4+1); f[#f~, 1]; \\ Michel Marcus, Aug 28 2013
(Magma) [#f eq 0 select 1 else f[ #f][1] where f is Factorization(2*n^4 + 1): n in [1..50]]; // Vincenzo Librandi, Feb 17 2015

Crossrefs

Sequence in context: A080987 A132561 A306002 * A006485 A003115 A053888

Adjacent sequences: A140535 A140536 A140537 * A140539 A140540 A140541

Keyword

easy,nonn

Author

Donald S. McDonald, Jul 06 2008

Extensions

Extended from a(16) on by R. J. Mathar, Aug 04 2008

Status

approved