一番上のやつk=100までで小数点以下228桁一致
https://www.hostmath.com/Show?Code=%5Cpi%3D2%5Csum_%7Bk%3D0%7D%5E%7B%5Cinfty%7D%5Cfrac%7B%5Cleft(2k%2B1%5Cright)!%5Cleft(4k%5Cright)!%5Cleft(290k%5E%7B3%7D%2B517k%5E%7B2%7D%2B286k%2B47%5Cright)%7D%7B4%5E%7Bk-1%7D%5Cleft(6k%2B5%5Cright)!%7D%5C%5C%5Cpi%3D%5Csum_%7Bk%3D0%7D%5E%7B%5Cinfty%7D%5Cfrac%7B2%5E%7Bk%2B3%7Dk!%5Cleft(3k%2B2%5Cright)!%5Cleft(4k%5Cright)!%5Cleft(40k%5E%7B2%7D%2B60k%2B23%5Cright)%7D%7B%5Cleft(2k%5Cright)!%5Cleft(6k%2B5%5Cright)!%7D
