# Inspired by Yan Shee

Algebra Level 4

$\large \sum_{n = 1} ^\infty \dfrac{n^2 + n}{2 \times 10^n}$

The value of the infinite series above can be expressed in the form $$\dfrac{a}{b}$$, where $$a$$ and $$b$$ are positive coprime integers. Find $$a+b$$ .

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