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Complete Archive

All mathematical explorations, puzzles, and problems

142857 - A remarkable number
Surprising properties of cyclic numbers.
2025 using primes
A nice Fiddler puzzle from Fabrice Bellard.
A Prime Sum Circle
And related puzzles solved using Graph Theory
A surprising polygon formula
Problem of the Week from Stan Wagon.
An Archery problem
A FiveThirtyEight Riddler puzzle.
Are You Clever Enough?
A FiveThirtyEight Riddler puzzle.
Bandit Algorithms For Website Optimization
This is my summary of the book - Bandit Algorithms for Website Optimization by John Myles White
Basics of network science with Networkx - 1
First instalment in the exploratory data analysis of graphs
Basics of network science with Networkx - 2
Second instalment in the exploratory data analysis of graphs
Beside the point
A wonderful geometric probability puzzle from Jane Street.
Breaking a slide rule into four pieces
A FiveThirtyEight Riddler puzzle.
Bug Byte
A fiendish puzzle from Jane Street.
Can You Bake The Biggest π?
A FiveThirtyEight Riddler puzzle.
Can You Bake The Radish Pie?
A FiveThirtyEight Riddler puzzle.
Can You Bat .299 In 299 Games?
A FiveThirtyEight Riddler puzzle.
Can you catch the cricket?
A FiveThirtyEight Riddler puzzle.
Can You Climb Your Way To Victory?
A FiveThirtyEight Riddler puzzle.
Can You Crack The Case Of The Crescent Moon?
A FiveThirtyEight Riddler puzzle.
Can You Crack The Case Of The Crystal Key?
A FiveThirtyEight Riddler puzzle.
Can You Cross Like A Boss?
A FiveThirtyEight Riddler puzzle.
Can You Cut The Perfect Pancake?
A FiveThirtyEight Riddler puzzle.
Can You Decipher The Secret Message?
A FiveThirtyEight Riddler puzzle.
Can You Draft A Riddler Fantasy Football Dream Team?
A FiveThirtyEight Riddler puzzle.
Can You Find A Matching Pair Of Socks?
A FiveThirtyEight Riddler puzzle.
Can You Find A Number Worth Its Weight In Letters?"
A FiveThirtyEight Riddler puzzle.
Can You Find An Extra Perfect Square?
A FiveThirtyEight Riddler puzzle.
Can you find the luckiest coin?
A FiveThirtyEight Riddler puzzle.
Can you flip the magic coin?
A FiveThirtyEight Riddler puzzle.
Can You Get A Haircut Already?
A FiveThirtyEight Riddler puzzle.
Can You Get The Paper Cut?
A FiveThirtyEight Riddler puzzle.
Can you help a frogger out?
A FiveThirtyEight Riddler puzzle.
Can You Hop Across The Chess Board?
A FiveThirtyEight Riddler puzzle.
Can You Hunt For The Mysterious Numbers?
A FiveThirtyEight Riddler puzzle.
Can You Navigate The One-Way Streets?
A FiveThirtyEight Riddler puzzle.
Can You Randomly Move The Tower?
A FiveThirtyEight Riddler puzzle.
Can You Reach The Summit First?
A FiveThirtyEight Riddler puzzle.
Can You Rescue The Paratroopers?
A FiveThirtyEight Riddler puzzle.
Can You Shuffle Numbers?
A FiveThirtyEight Riddler puzzle.
Can You Skillfully Ski The Slopes?
A FiveThirtyEight Riddler puzzle.
Can You Slay The Puzzle Of The Monsters’ Gems?
A FiveThirtyEight Riddler puzzle.
Can You Slice The Ice?
A FiveThirtyEight Riddler puzzle.
Can You Solve The Vexing Vexillology?
A FiveThirtyEight Riddler puzzle.
Can You Solve This Astronomical Enigma?
A FiveThirtyEight Riddler puzzle.
Can You Solve This Elevator Button Puzzle?
A FiveThirtyEight Riddler puzzle.
Can you stick it to the genie?
A FiveThirtyEight Riddler puzzle.
Can You Survive Squid Game?
A FiveThirtyEight Riddler puzzle.
Can You Systematically Solve A Friday Crossword?
A FiveThirtyEight Riddler puzzle.
Can You Tell When The Snow Started?
A FiveThirtyEight Riddler puzzle.
Can You Time The Stoplight Just Right?
A FiveThirtyEight Riddler puzzle.
Can You Win Riddler Jenga?
A FiveThirtyEight Riddler puzzle.
Can You Win The Penalty Shootout?
A FiveThirtyEight Riddler puzzle.
Centered Pentagonal Number
A FiveThirtyEight Riddler puzzle.
Connected paths in a 2 x n grid
A sweet problem involving recurrence relation.
Counting triangles in a graph
Various techniques for counting and listing triangles in a graph.
Dancer pairs
A wonderful combinatorics puzzle from Jane Street.
Delirious Ducks
A FiveThirtyEight Riddler puzzle.
Different Distances Puzzle
A puzzle about placing counters on a checkerboard with different distances
Dodecahedron Quintomino puzzle
A beautiful puzzle from John Conway.
En Garde! Can You Win The Fencing Relay?
A FiveThirtyEight Riddler puzzle.
Evolutionary Computation
The power of the technique illustrated with a couple of examples.
Expected distance of a random point from the centre of a regular polygon with circum radius one
Calculating expectation analytically and computationally.
Fixed Income with Python - 1
Basics of fixed income instruments.
Flowfree
Solution using constraint programming.
Hamiltonian Cycles
A couple of hamiltonian cycles that I stumbled upon.
Happy Birthday Sharada!
A geeky gift for my beautiful wife on her birthday.
Help Us Find These Missing Pieces
A FiveThirtyEight Riddler puzzle.
How Do You Like Them Rectangles?
A FiveThirtyEight Riddler puzzle.
How Long Will It Take To Blow Out The Birthday Candles?
A FiveThirtyEight Riddler puzzle.
How Long Will Your Smartphone Distract You From Family Dinner?
A FiveThirtyEight Riddler puzzle.
How Low Can You Roll?
A FiveThirtyEight Riddler puzzle.
How Many Cars Will Get Stuck In Traffic?
A FiveThirtyEight Riddler puzzle.
How Many Friends Are On The Riddler Social Network?
A FiveThirtyEight Riddler puzzle.
How Many Ways Can You Build A Staircase?
A FiveThirtyEight Riddler puzzle.
How Many Ways Can You Raid The Candy Shop?
A FiveThirtyEight Riddler puzzle.
Ikigai
The ten rules.
Interesting Questions
A collection of intriguing questions from multiple sources.
Inversion - A beautiful idea from Geometry
A few problems illustrating the power of inversion.
Investment Management with Python - 1
Fundamentals of Return and Risk
Investment Management with Python - 2
Beyond the Gaussian case:Extreme risk estimates
Investment Management with Python - 3
Portfolio Optimization and Efficient Frontier
Islamic Geometric Patterns
My implementation of some of the ideas in Python from the book - Islamic Geometric Patterns
Knights on a chess board
The power and beauty of Markov Chains.
Langford problem
Three different solutions.
Linkedin Tango Puzzle
Solving using the fantastic Z3 library.
Little Cubes
A FiveThirtyEight Riddler puzzle.
Loading IMDB data into SQLite in 200 lines of Python
You will be surprised how incredibly useful and powerful SQLite is.
Maximizing the length of the trajectory of a projectile
A puzzle from Fiddler.
My Dad's 'mystery cold'
My Sherlock Holmes moment.
Night Falls. A Storm Rolls In. Can You Cross The River?
A FiveThirtyEight Riddler puzzle.
No Isosceles Triangles For You!
A FiveThirtyEight Riddler puzzle.
Number Hooks
Using the fantastic Z3 to solve a nice puzzle from Jane Street.
On camels and straws
A famous puzzle about probability and expectation involving sum of uniform random variables.
Points on a circle
A FiveThirtyEight Riddler puzzle.
Probability and vitamin pills
A FiveThirtyEight Riddler puzzle.
Random Tic Tac Toe
A FiveThirtyEight Riddler puzzle.
Riddle of the pilgrims
Solution using integer programming.
Rolling Cube
A beautiful puzzle from John Harris.
Running Total of a Die
Solved using two different approaches.
Same number on all the dies
A FiveThirtyEight Riddler puzzle.
Should The Grizzly Bear Eat The Salmon?
A FiveThirtyEight Riddler puzzle.
Should You Pay $250 To Play This Casino Game?
A FiveThirtyEight Riddler puzzle.
Should You Shoot Free Throws Underhand?
A FiveThirtyEight Riddler puzzle.
Simulated Annealing
The power of the technique illustrated with a couple of examples.
Solving 3-In-A-Row using Z3
Using the fantastic Z3 for fun.
Solving a Cryptarithmetic puzzle using Z3
Using the fantastic Z3 for fun.
Solving Calcudoku using Z3
Using the fantastic Z3 for fun.
Solving Kakurasu using Z3
Using the fantastic Z3 for fun.
Solving Kakuro using Z3
Using the fantastic Z3 for fun.
Solving Numbrix using Z3
Using the fantastic Z3 for fun.
Solving Ostomachion using Z3
A FiveThirtyEight Riddler puzzle.
Solving Skyscrapers using Z3
Using the fantastic Z3 for fun.
Solving Squares Sudoku using Z3
Using the fantastic Z3 for fun.
Solving the Jumping Julia Maze
A step by step guid using Python's NetworkX library.
Some Off Square
Solved using two different approaches.
SQL Practice Problems - Advanced
Solutions to advanced problems from the book - SQL Practice Problems
SQL Practice Problems - Basic
Solutions to basic problems from the book - SQL Practice Problems.
SQL Practice Problems - Intermediate
Solutions to intermediate problems in the book - SQL Practice Problems.
The Puzzle Of Misanthropic Neighbors?
A FiveThirtyEight Riddler puzzle.
Unusual Crossword
An unusual crossword based on the first 30 digits of pi.
What Are The Odds You’d Already Have My Number?
A FiveThirtyEight Riddler puzzle.
When Will The Arithmetic Anarchists Attack?
A FiveThirtyEight Riddler puzzle.
Where Will The Seven Dwarfs Sleep Tonight?
A FiveThirtyEight Riddler puzzle.
Who Betrayed Dune’s Duke Leto?
A FiveThirtyEight Riddler puzzle.
Who owns the fish?
Using the fantastic Z3 for fun.
Who Steals The Most In A Town Full Of Thieves?
A FiveThirtyEight Riddler puzzle.
Who Wants To Be A Riddler Millionaire?
A FiveThirtyEight Riddler puzzle.
Will Riddler Nation Win Gold In Archery?
A FiveThirtyEight Riddler puzzle.
Will Someone Be Sitting In Your Seat On The Plane?
A FiveThirtyEight Riddler puzzle.
Will The Neurotic Basketball Player Make His Next Free Throw?
A FiveThirtyEight Riddler puzzle.
Will You Be A Ghostbuster Or A World Destroyer?
A FiveThirtyEight Riddler puzzle.
Work A Shift In The Riddler Gift Shop
A FiveThirtyEight Riddler puzzle.
You Have $1 Billion To Win A Space Race. Go.
A FiveThirtyEight Riddler puzzle.
Combinatorics Problem
Challenging combinatorics puzzle
PDF
Strava Analysis
Mathematical analysis of Strava walking data
PDF