Regex for Alpha Numeric and some special characters

I have a input controller which I want to allow only Alpha Numeric values and -,@ and # special characters, I have using the following input-filter, input-filter='[A-Za-z0-9 -_@#]{1,20}', it is allowing but Alpha Numeric values properly but not allowing special characters, -,@ and #, what am I doing wrong, can somebody please help me - thanks a lot.