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Sum

What is
$$\sum_{i=1}^{\infty}\frac{1}{i 2^i}$$
?

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Sunday Afternoon Maths LXVII

Coloured weights
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Advent calendar 2018

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Cryptic crossnumber #2

Sunday Afternoon Maths LXV

Cryptic crossnumber #1
Breaking Chocolate
Square and cube endings

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