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(1/15 1/35 1/63 1/99)*2

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(1/15 1/35 1/63 1/99)*2
(1/15 1/35 1/63 1/99)*2
1/3+1/15+1/35+1/63+1/99+1/143
=1/2×(1-1/3)+1/2×(1/3 -1/5)+1/2×(1/5-1/7)+1/2×(1/7-1/9)+1/2×(1/9-1/11)+1/2×(1/11-1/13)
=1/2×(1-1/3+1/3-1/5······+1/11-1/13)
=1/2×(1-1/13)
=1/2×12/13
=6/13
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