Its 179,700.
Hoorey for math.
Formula:
(L squared - F squared + F + L) divided by 2.
L=Last number, F = First number
(599 squared - 1 squared + 599 + 1) divided by 2
= (358,801 - 1 + 599 + 1) divided by 2
= (358,800 + 600) divided by 2
= 359,400 divided by 2
= 179,700.
I think.