OFFSET
1,1
COMMENTS
Any term is divisible by the square of a base 5 Wieferich prime (A123692).
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..879 (terms below 10^12)
PROG
(PARI) forcomposite(n=1, 1e9, if(Mod(5, n)^(n-1)==1, if(!issquarefree(n), print1(n, ", "))))
CROSSREFS
KEYWORD
nonn
AUTHOR
Felix Fröhlich, Aug 18 2014
STATUS
approved