Arima Yoriyuki

In this Japanese name, the surname is Arima.

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 $\pi$ and its square, $\pi ^{2}$. In 1766, he found the following rational approximation of $\pi$, correct to 29 digits:

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

Further reading

• Döll, Steffen; Hinz, Andreas M. (2018). "Kyū-renkan – the Arima sequence". In Ogawa, T.; Morimoto, M. (eds.). Mathematics of Takebe Katahiro and History of Mathematics in East Asia. Advanced Studies in Pure Mathematics. Vol. 79. Tokyo: Mathematical Society of Japan. pp. 321–335.