A104132 Largest prime factor of pip(n)^pip(n)-1 where pip(n) is the n-th prime-indexed prime.

13, 71, 1806113, 2699538733, 568972471024107865287021434301977158534824481, 5926187589691497537793497756719

Offset: 1

Author

Cino Hilliard, Mar 06 2005

Keywords

• nonn
• less

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10

Crossrefs

Cf. A006450, A006530, A006486, A048861, A104131, A214812.

Programs

Mathematica

lpf[n_]:=Module[{p=Prime[Prime[n]]},FactorInteger[p^p-1][[-1,1]]]; Array[lpf,6] (* Harvey P. Dale, Nov 09 2017 *)

PARI

piptopipm1(n) = { local(x, y); for(x=1, n, y=pip(x)^pip(x)-1; print1(bdiv(y)", "); ) }
pip(n) = { return(prime(prime(n))) }
bdiv(n) = { local(x); x=ifactor(n); return(x[length(x)]) }
ifactor(n, m=0) = { local(f, j, k, flist); flist=[]; f=Vec(factor(n, m)); for(j=1, length(f[1]), for(k = 1, f[2][j], flist = concat(flist, f[1][j]) ); ); return(flist) }

Formula

a(n) = A006530(A048861(A006450(n))). - Amiram Eldar, May 23 2020

Extensions

a(6) corrected by Harvey P. Dale, Nov 09 2017