In the range of 85 to 645 there are 645-85+1=561 numbers.
If you take the first 21 ones you get a sum of 84*21*22/2 = 19404;
if you get the first 22 ones you get a sum of 84*22*23/2 = 21252;
and so on.
In my opinion there is only one way to get 76 numbers summarizing 20000:
- accepting duplicates by running VBA code.
Is it ok for you?

Bruno