Can I send math subject GRE scores to programs that do not require them?
You can still send it in. You can always add more information to your application, but there is no guarantee that they will consider it. I know a few schools have stopped asking for GRE subject scores because they don't feel that it's a good way to predict performance, and if that is the case they will not look at it. Assuming you have a good score, it will not count against you.