what is this called in math {15, 16, 17, 21}
In mathematics, the set `{15, 16, 17, 21}` refers to a collection of distinct elements or numbers, where the order of the elements does not matter, and duplicates are not allowed. In this case, the set contains the four integers 15, 16, 17, and 21.
Sets are typically denoted using curly braces `{}` with the elements listed inside, and they are a fundamental concept in various branches of mathematics, including set theory, number theory, and algebra. The particular set `{15, 16, 17, 21}` has no special name or significance on its own beyond being an example of a finite set with these elements.