# It looks like $$e^x$$

Calculus Level 3

If the value of $$\displaystyle\sum_{n=0}^{\infty}\frac{n^2x^n}{n!}$$ is $$(ax^2+bx+c)e^x$$, where $$a$$, $$b$$, and $$c$$ are constants, enter the value of $$123a+456b+789c$$.

• $$\displaystyle e^x=\sum_{n=0}^\infty\frac{x^n}{n!}$$