Add a sequence of #'s n+n-1 to n

[Tony]

I am looking for a formula that is similiar to factorial
(eg 10!) but is for addition.

I want to use this in excel but can not find the
formula. It would be (n + n-1) to the nth I believe.

thank you

 

[Alan Beban]

I am looking for a formula that is similiar to factorial
(eg 10!) but is for addition.

I want to use this in excel but can not find the
formula. It would be (n + n-1) to the nth I believe.

thank you

n*(n+1)/2

Alan Beban