cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-2 of 2 results.

A088730 Numbers of the form p^p - 1, where p is a prime.

Original entry on oeis.org

3, 26, 3124, 823542, 285311670610, 302875106592252, 827240261886336764176, 1978419655660313589123978, 20880467999847912034355032910566, 2567686153161211134561828214731016126483468
Offset: 1

Views

Author

Cino Hilliard, Nov 23 2003

Keywords

Comments

Sum of reciprocals = 0.3721161884983118696170302604..

Examples

			a(1) = 3 because the first prime is 2 and 2^2 - 1 = 3.
a(2) = 26 because the second prime is 3 and 3^3 - 1 = 26.
a(3) = 3124 because the fifth prime is 5 and 5^5 - 1 = 3124.
		

Crossrefs

Cf. A051674, A088807, A125135 (factorizations).

Programs

Formula

a(n) = A051674(n) - 1. - R. J. Mathar, Jul 15 2007

Extensions

More terms from Ray Chandler, Feb 21 2004

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

Original entry on oeis.org

3, 13, 71, 4733, 1806113, 1803647, 2699538733, 109912203092239643840221, 1920647391913, 549334763, 568972471024107865287021434301977158534824481, 41903425553544839998158239, 5926187589691497537793497756719, 19825223972382274003506149120708429799166030881820329892377241, 194707033016099228267068299180244011637
Offset: 1

Views

Author

N. J. A. Sloane, Jul 31 2012

Keywords

Crossrefs

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
Showing 1-2 of 2 results.