摘要：
数论黑科技 1 阅读全文
posted @ 2024-07-23 09:34
weilycoder
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摘要：
The arithmetic derivative is defined by
$p^\prime = 1$ for any prime $p$;
$(ab)^\prime = a^\prime b + ab^\prime$ for all integers $a, b$ (Leibniz rule).
For example, $20^\prime = 24$.
Find $\sum \gcd(k,k^\prime)$ for $1 \lt k \le 5 \times 10^{15}$. 阅读全文
posted @ 2024-07-23 06:57
weilycoder
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