The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS"). Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A074478 Largest prime factor of 5^n + 1. 6
 2, 3, 13, 7, 313, 521, 601, 449, 11489, 5167, 9161, 5281, 390001, 38923, 234750601, 7621, 29423041, 41540861, 6597973, 213029, 632133361, 7603, 1030330938209, 42272797713043, 152587500001, 50150933101, 83181652304609, 16018507 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 LINKS Amiram Eldar, Table of n, a(n) for n = 0..451 (terms 0..100 from Vincenzo Librandi) S. S. Wagstaff, Jr., The Cunningham Project FORMULA a(n) = A006530(A034474(n)). - Michel Marcus, Jul 09 2016 EXAMPLE 5^11 + 1 = 48828126 = 2*3*23*67*5281, so a(11) = 5281. MATHEMATICA Table[FactorInteger[5^n + 1][[-1, 1]], {n, 0, 30}] (* Bruno Berselli, Aug 23 2013 *) PROG (PARI) for(n=0, 30, v=factor(5^n+1); print1(v[matsize(v)[1], 1], ", ")) (MAGMA) [Maximum(PrimeDivisors(5^n+1)): n in [0..30]]; // Vincenzo Librandi, Jul 09 2016 CROSSREFS Cf. A002587 (largest prime factor of 2^n + 1), A074479 (largest prime factor of 5^n - 1), A074476 (largest prime factor of 3^n + 1), A227575 (largest prime factor of 7^n + 1). Cf. A006530, A034474. Sequence in context: A192362 A057776 A110362 * A046421 A132365 A129671 Adjacent sequences:  A074475 A074476 A074477 * A074479 A074480 A074481 KEYWORD nonn AUTHOR Rick L. Shepherd, Aug 23 2002 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 1 16:44 EST 2020. Contains 338846 sequences. (Running on oeis4.)