mscroggs.co.uk
mscroggs.co.uk

subscribe

Puzzles

Sum

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

Show answer & extension

Archive

Show me a random puzzle
 Most recent collections 

Advent calendar 2024

Advent calendar 2023

Advent calendar 2022

Advent calendar 2021


List of all puzzles

Tags

square grids decahedra dice consecutive numbers multiples squares crossnumbers geometric mean range cube numbers triangle numbers dominos square roots division pascal's triangle doubling square numbers medians digits cards advent spheres irreducible numbers time remainders partitions sets combinatorics dodecagons perimeter binary odd numbers sums folding tube maps pentagons polynomials scales quadrilaterals floors people maths volume dates star numbers albgebra axes averages arrows polygons wordplay coins probabilty balancing ave rugby means lines surds sum to infinity ellipses neighbours shape chalkdust crossnumber powers matrices digital clocks books cryptic crossnumbers tournaments symmetry indices mean routes grids christmas regular shapes elections multiplication bases taxicab geometry fractions clocks median speed hexagons logic games factors probability triangles coordinates even numbers 3d shapes geometric means crosswords graphs menace differentiation algebra numbers grids geometry the only crossnumber integration chess determinants rectangles money complex numbers digital products cryptic clues sequences tangents addition cubics chocolate products circles 2d shapes palindromes shapes integers perfect numbers parabolas area tiling consecutive integers planes angles quadratics expansions proportion numbers trigonometry functions unit fractions percentages prime numbers factorials sport colouring calculus number gerrymandering

Archive

Show me a random puzzle
▼ show ▼
© Matthew Scroggs 2012–2025