What is the integral that equals lim_n⭢∞_i=1^n(1/n)[3(1+i/n)^3+3]

What is the integral that equals limnΣi=1n(1n)[3(1+in)3+3]\lim_{n\rightarrow\infty}\Sigma_{i=1}^n\left(\frac{1}{n}\right)\left[3\left(1+\frac{i}{n}\right)^3+3\right]
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