A214812 Largest prime factor of (p^p-1)/(p-1) where p = prime(n).

3, 13, 71, 4733, 1806113, 1803647, 2699538733, 109912203092239643840221, 1920647391913, 549334763, 568972471024107865287021434301977158534824481, 41903425553544839998158239, 5926187589691497537793497756719, 19825223972382274003506149120708429799166030881820329892377241, 194707033016099228267068299180244011637

Offset: 1

Author

N. J. A. Sloane, Jul 31 2012

Keywords

• nonn

Links

• Daniel Suteu, Table of n, a(n) for n = 1..33
• T. S. Motzkin, Sorting numbers for cylinders and other classification numbers, in Combinatorics, Proc. Symp. Pure Math. 19, AMS, 1971, pp. 167-176. [Annotated, scanned copy]

Crossrefs

Cf. A001039, A088807, A125135, A212552, A214811.

Programs

Mathematica

FactorInteger[#][[-1,1]]&/@Table[(p^p-1)/(p-1),{p,Prime[Range[15]]}] (* Harvey P. Dale, Aug 27 2016 *)

PARI

a(n) = my(p=prime(n)); vecmax(factor((p^p-1)/(p-1))[,1]); \\ Daniel Suteu, May 26 2022

Formula

a(n) = A006530(A001039(n)). - Daniel Suteu, May 26 2022