Definition
Sequence
A sequence is an ordered list of numbers or objects, with each item in a numbered position.
What it means
Read a sequence in order. Swapping two terms makes a different sequence, even if the same items are still present. A sequence may follow a visible rule, but being ordered is what makes it a sequence.
Remember it
A sequence is a list with numbered places.
Example
In the sequence 12, 7, 12, 4, the terms at positions 1 and 3 are both 12. Reordering it as 12, 12, 7, 4 makes a different sequence.
Watch for
A set ignores order and repeated entries; a sequence keeps both the order and every repeated term.
Common mix-up
A sequence does not have to increase, and it does not need an obvious simple pattern.
Exact meaning
A sequence is an ordered list of terms in which each term has a position; the order is part of the mathematical information.