The Special Characters palette includes many mathematical symbols, but I cannot seem to find [blackboard bold](http://en.wikipedia.org/wiki/Blackboard_bold) versions of N, R, and Z, which are commonly used to denote the set of (respectively) the natural numbers, real numbers, and integers.

Right now, when I use the Special Characters palette and configure the Unicode section, and then look for the mathematical symbols, I find blackboard versions of A, B, and others, but inexplicably, certain characters including the N, R, and Z are *missing*. Here is a screenshot to show what I mean:

![enter image description here](https://i.stack.imgur.com/lHf0l.png)

Are the blackboard characters available somehow, and I am missing something really obvious?