｢1/n² Σn=1,∞｣
= 1/1² + 1/2² + (1/3²+1/4²) + (1/5²+1/6²+1/7²+1/8²) + ...
< 1/1² + 1/2 + (1/2²+1/2²) + (1/4²+1/4²+1/4²+1/4²) + ...
┄
1/(2˄(k−2))²·2˄(k−2)
= 1/2˄(2k−4)·2˄(k−2)
= 1/2˄(2k−4−k+2)
= 1/2˄(k−2)
┄
= 1 + 1/2˄0 + 1/2˄1 + 1/2˄2 + ...
= 1 + ｢(1/2)˄i Σi=0,∞｣
= 1 + 1/(1−1/2)
= 3
