# Binomial Summations 6

Algebra Level 5

If the expansion of $(1+x+2x^2)^{20}$ is equal to $a_0 + a_1 x+ a_2 x^2 + \cdots + a_{40} x^{40}$ for constants $a_0,a_1, \ldots , a_{40}$, compute

$\left \lceil \dfrac1{10^8} \sum_{r=0}^{19} a_{2r} \right \rceil .$

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