OFFSET
1,1
COMMENTS
Up to now only two primes p such that p^2 divides 2^(p-1)-1 are known (these two are Wieferich primes, see A001220).
EXAMPLE
From Reinhard Zumkeller, May 14 2010: (Start)
a(1)^2 = 9 = A177855(5);
a(2)^2 = 49 = A177855(14);
a(3)^2 = 169 = A177855(30);
a(4)^2 = 1194649 = A177855(1843). (End)
CROSSREFS
KEYWORD
nonn,fini,full
AUTHOR
Artur Jasinski, Jan 30 2010
EXTENSIONS
Keyword full added by Reinhard Zumkeller, May 14 2010
STATUS
approved