Arima Yoriyuki

Arima Yoriyuki (有馬 頼徸; December 31, 1714 – December 16, 1783) was a Japanese mathematician of the Edo period. He was the lord of Kurume Domain.

He approximated the value of ${\displaystyle \pi }$ and its square, ${\displaystyle \pi ^{2}}$. In 1766, he found the following rational approximation of ${\displaystyle \pi }$, correct to 29 digits:^[1][2]

${\displaystyle \pi \approx {\frac {428224593349304}{136308121570117}}=3.14159265358979323846264338327(569...).}$