Ordered collections with $a_1$ as first element, $a_2$ as second element, $\dots$, and $a_n$ as nth element, denoted $(a_1, a_2, \dots, a_n)$
Ordered collections with $a_1$ as first element, $a_2$ as second element, $\dots$, and $a_n$ as nth element, denoted $(a_1, a_2, \dots, a_n)$