title: Problem 968
date: 2025/11/08 17:00:00
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# [Problem 968](https://projecteuler.net/problem=968)
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[Xem đề gốc (tiếng Anh)](https://projecteuler.net/problem=968)

## **Tổng 5 chiều**

$f(n) = \sum_{a_1+\ldots+a_5=n} a_1 a_2 a_3 a_4 a_5$. Tính $\sum_{n=5}^{10^{12}} f(n) \pmod{10^9+7}$.

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