说不尽的 π —— π 的近似计算

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1. Riemann zeta function

π26=∑n=1∞1n2=112+122+132+142+⋯

np.sqrt(6 * np.sum(1./np.arange(1, 100000)**2))

2. Gregory–Leibniz series

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4 * sum((-1.)**(i+1)/(2*i-1) for i in range(1, 100000))