Function with a hash I have a question involving a function:
$\tau(n) := $#{$d\in\Bbb{Z}>0|$d divides n}
The hash symbol before the first bracket is confusing me, I don't know what this means. And could you please give an example for if I was to substitute in a value for n.
Thanks

It could be the cardinality (number of elements) of the set behind the hash mark. The hash symbol is also used as abbreviation for number: link.
