Counting unique values in a table column

I have a table accounts "Account Numbers" and at the bottom of the table I would like to provide a value that shows the number of unique account numbers in the column. Please note that this is a table and not a list.

Account Number
0233
0233
0234
4432
4333
4432
4415
4415

I am using Excel 365 ProPlus. Is there a function I can place at the bottom of the column for this table that will count the number of unique account numbers? Would this function still work if the account numbers were filtered in some way (e.g. account numbers that only begin with the number 4,etc.?

Thanks in advance for the help with this!

MGTexas123

=SUM(1/COUNTIF(A3:A10,A3:A10)) array formula

Originally Posted by tim201110

=SUM(1/COUNTIF(A3:A10,A3:A10)) array formula

Thanks Tim for your help with this. Is there a way to do this without an array formula or cell references? Something like countif(1/(column header name in table)) ?