OFFSET
1,1
COMMENTS
The prime p divides 3^p - 2^p - 1. Quotients (3^p - 2^p - 1)/p, where p = Prime[n], are listed in A127071. - Alexander Adamchuk, Jan 31 2008
a(7) > 10^9. [From D. S. McNeil, Mar 16 2009]
MATHEMATICA
Do[ n=Prime[k]; f=PowerMod[3, n, n^2] - PowerMod[2, n, n^2] - 1; If[ IntegerQ[ f/n^2 ], Print[n] ], {k, 1, 100000} ]
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
Alexander Adamchuk, May 05 2007
EXTENSIONS
2 more terms found by Ryan Propper, Jan 01 2008.
Incorrect a(7), a(8) removed by D. S. McNeil, Mar 16 2009. (The old version was 2,3,7,179,619,17807,135433,1376257.)
STATUS
approved