The nth term will be n²×(2n + 1)

The generalized equation be

We know by property that:

∑axⁿ + bx^{n - 1} + cx^{n - 2}…….d₀=a∑xⁿ + b∑x^{n - 1} + c∑x^{n - 2}…….. + d₀∑1

Thus

………(1)

We know

Substituting the values in (1)

=

=

=

=