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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

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Cryptic crossnumber #2

Sunday Afternoon Maths LXV

Cryptic crossnumber #1
Breaking Chocolate
Square and cube endings

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

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