If the sum of the first nnn terms is Sn=n2+2nS_n = n^2 + 2nSn=n2+2n, what is the 10th10^{th}10th term a10a_{10}a10?
a10=19a_{10} = 19a10=19
a10=21a_{10} = 21a10=21
a10=120a_{10} = 120a10=120
a10=140a_{10} = 140a10=140