What is the nth term ana_nan of the series 1+4+9+16+...1 + 4 + 9 + 16 + ...1+4+9+16+...?
an=na_n = nan=n
an=2na_n = 2nan=2n
an=n2a_n = n^2an=n2
an=n+1a_n = n+1an=n+1