355./113
3.1415929203539825
99733./31746
3.1415926415926414
833719./265381
3.1415926535810779

http://www.finetune.co.jp/~lyuka/technote/pi/pi-chudnovsky.png
k = 0 のときで
4270934400./(13591409.*sqrt(10005))
3.1415926535897345