title: Problem 813
date: 2022/10/22 12:00:00
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# [Problem 813](https://projecteuler.net/problem=813)
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[Xem đề gốc (tiếng Anh)](https://projecteuler.net/problem=813)

## **Lũy thừa XOR**

$f(a, b) = a^{a \oplus b}$. Tính $\sum_{a,b=0}^{10^6} f(a,b) \pmod{10^9+7}$.

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