利用以下公式,计算 PI 至小数点后s位 oo --- n L * PI \ (-1) 4 * L L -------- = / [ ------- ( ---------- - -------------- ) ] 4 --- 2n+1 5^(2n+1) 239^(2n+1) n=0 L : 为一大整数 10^s PI : 圆周率-Using the following formula to calculate PI to s

In this work the interaction forces between linear Halbach arrays are analytically calculated thanks to our recent development 3D exact calculation of forces between two cuboï dal magnets with parallel and perpendicular magnetization. W