A finite, increasing sequence of integers 
such that
 |
A sequence is a Giuga sequence iff it satisfies
 |
for 
,
..., 
.
There are no Giuga sequences of length 2, one of length 3 (
), two of length 4 (
and 
), 3 of length 5 (
, 
, and 
), 17 of length 6, 27 of length 7, and hundreds
of length 8. There are infinitely many Giuga sequences. It is possible to generate
longer Giuga sequences from shorter ones satisfying certain properties.
