thumb|Arima Yoriyuki
was a Japanese mathematician of the Edo period. He was the lord of Kurume Domain.
He approximated the value of <math>\pi</math> and its square, <math>\pi^2</math>. In 1766, he found the following rational approximation of <math>\pi</math>, correct to 29 digits:
:<math>\pi\approx\frac{428224593349304}{136308121570117}=3.14159265358979323846264338327(569...).</math>