An n-tuple (x1,...,xn) is an ordered list of n sets. It can be constructed in several ways. A popular definition is the original set x1 for n=1 and the ordered pair ((x1,...,xn-1),xn) otherwise.
Klick on the ordered pair ( 258, 215 ) or the natural number 17 to see how it may be defined as a set.
(258, 215, 17) = ( ( 258, 215 ), 17 )