Possible Duplicate:
What is the term for a factorial type operation, but with summation instead of products?
I don't technically know the mathematical term, but imagine:
X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X
taking the last row that holds 10 elements, the total will be:
10 + 9 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1
witch totals 55
just like there is the factor sign 10!
that tells us the same but multiplying the numbers, is there a technical term / function, to by other means calculate the total 55?