What is the formula for a sum of 2000+2200+2400+2600+2800...n

If you know the formatting for an excel spreadsheet that would be awesome!

Sn = a1 + a2 + a3 + ... + an = n(a1 + an)/2 = n[2a1 + (n-1)d]/2
With: a1 = 2000, d = 200
So, Sn = n[4000 + 200(n-1)] / 2 = 100n(19 + n)

Test: with n = 2: S2 = 2000 + 2200 = 4200
or S2 = 100*2(19 + 2) = 4200

with n=3: S3 = 2000 + 2200 + 2400 = 6600
or S3 = 100*3(19+3) = 6600

Summary: Sn = 2000 + 2200 + 2400 + ... + [2000 + 200(n-1)] = 100n(19+n)

Sn = n*(a1 + an)/2

Sn = sum of nth terms
a1 = first term
an = nth term