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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
Not Roman numerals

Advent calendar 2018

Sunday Afternoon Maths LXVI

Cryptic crossnumber #2

Sunday Afternoon Maths LXV

Cryptic crossnumber #1
Breaking Chocolate
Square and cube endings

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cryptic crossnumbers games christmas grids mean symmetry 3d shapes surds palindromes shapes integers floors menace geometry number means rectangles scales percentages circles crosswords perfect numbers calculus proportion doubling probability wordplay time quadratics indices shape multiples graphs dice cryptic clues taxicab geometry coins triangles perimeter arrows factorials dodecagons books bases folding tube maps rugby volume routes colouring hexagons ellipses people maths functions addition factors chalkdust crossnumber trigonometry triangle numbers star numbers square numbers multiplication sequences cube numbers complex numbers money area remainders differentiation sum to infinity balancing chocolate averages 2d shapes lines clocks division crossnumbers spheres dates speed regular shapes partitions coordinates cards numbers chess logic digits prime numbers pascal's triangle ave unit fractions advent square roots integration algebra sums angles fractions sport odd numbers planes parabolas probabilty irreducible numbers polygons squares

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