A247230 Maximum of the greatest prime factors of (i^prime(n)-1)/(i-1), when i runs through all integers in [2, prime(n)].

3, 13, 71, 55987, 12207031, 16148168401, 50544702849929377, 109912203092239643840221, 26552618219228090162977481, 582595509837473004489665028935473297399, 568972471024107865287021434301977158534824481, 4673016293261684390446904937094157950067612234753

Offset

1,1

Comments

If in the definition "maximum" is replaced with "minimum," then we obtain A247229.

Links

Table of n, a(n) for n=1..12.

Formula

a(n)==1 (mod prime(n)).

Prog

(PARI) a(n) = {maxi = 0; p = prime(n); for (i=2, p, f = factor((i^p-1)/(i-1)); gpf = f[#f~, 1]; if (! maxi, maxi = gpf, maxi = max(maxi, gpf)); ); maxi; } \\ Michel Marcus, Dec 09 2014

Crossrefs

Cf. A247216, A247229.

Sequence in context: A059032 A214812 A188051 * A047159 A086662 A293195

Adjacent sequences: A247227 A247228 A247229 * A247231 A247232 A247233

Keyword

nonn

Author

Vladimir Shevelev, Nov 27 2014

Extensions

More terms from Peter J. C. Moses, Nov 27 2014

Status

approved