How do you do a summation series of excel?

[Stalker0]

For instance, I set a cell to equal 6.

I want a formula that will do 6+5+4+3+2+1.

If 5 it does 5+4+3+2+1

etc.

 

[Ferret]

I tried an idea I had but it didn't work.... Sorry i can't help.

Wait, duh... there is a formula for triangle numbers, feed that in and have N equal to the cell you want.

1/2n(n+1) should work...