Originally Posted by

**AfterShock** For a specific algorithm, I figured that in the algorithm, for:

n = 3, the answer is 1

n = 4, the answer is 4

n = 5, the answer is 10

n = 6, the answer is 20

n = 7, the answer is 35

n = 8, the answer is 56

n = 9, the answer is 84

n = 10, the answer is 84

n = 11, the answer is 120

And so forth.

I need the sum of all numbers in general, for n >= 3.

I can't quite see what the general formula would be. It initially appeared to be a geometric series.

So,

1 + 4 + 10 + 20 + 35 + 56 + 84 + 120...

It goes up in increments of: 3, 6, 10, 15, 21, 28, 36

Where:

3 to 6 --> 3

6 to 10 --> 4

10 to 15 --> 5

15 to 21 --> 6

x to y --> n + 1, where is n is the previous amount it went up by.

Anyone see the generic formula/series?

Thanks.