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Count the primes resulting from changing one digit of a number
If you start with the number 24 and seek primes by changing a single digit, you can find two: 23 and 29. If you start with 130, ...

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Solve an easy binary puzzle
A binary puzzle presents a square grid (or matrix) of cells in which each cell must be 0 or 1. The finished puzzle must follow t...

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Convert integers from base 10 to proper primary notation
This problem is the companion to Cody Problem 60782. The proper primary system of expressing numbers has three digits: m, x, and...

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Indicate how the Prague astronomical clock strikes the hours
The astronomical clock in Prague has a bell that rings 1, 2, 3, or 4 times. The number of strokes follows the sequence 123432123...

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Play Hocus Focus
The card game Hocus Focus starts by placing twelve cards with wizards face up on a table. The characteristics of the wizards tha...

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Express integers in negabinary
Negabinary numbers are written in base -2. For example, the negabinary number 11010 is , or 6 in base 10. In a similar way, -3 i...

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Reverse Boggle
Description In the classic Parker Brothers game Boggle, players find words from a 4x4 game board of letters. This exercise is t...

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Complete hydraulic geometry relations
Hydraulic geometry relations express the velocity , width , and depth of a river as a function of the discharge (or flow) , whi...

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Identify de Polignac numbers
The numbers 125 and 329 can be written as the sum of a prime and a power of 2. For example, , and . The numbers 127 and 331, whi...

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Goldbach's marginal conjecture - Write integer as sum of three primes
Goldbach's strong conjecture states that every even integer greater than 2 can be expressed as the sum of two primes. For exampl...

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Lah Numbers
Create a square lower diagonal matrix containing the first n Lah number coefficients. In mathematics, the Lah numbers are coeffi...

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Find the next Fibonacci number
In the sequence of Fibonacci numbers, every number is the sum of the two preceding ones: 1, 1, 2, 3, 5, 8, 13, 21, 34, 55...

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Determine whether a number is a Ludic prime
Ludic numbers are formed by a sieve. Start with a list of the positive integers. Skip 1 and start with 2. Then delete every seco...

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Identify points inside a Reuleaux triangle
Write a function to identify points that lie in or on a Realeaux triangle, which is a curve of constant width. The input to the ...

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Find the closest canyon prime
My wife and I celebrated our honeymoon and most recent anniversary in Yellowstone and Grand Teton National Parks. After returnin...

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Build a block Toeplitz matrix
A symmetric block Toeplitz matrix has the form, where the are compatibly-sized matrices. Write a routi...

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List composite numbers that do not contain their prime factors as substrings
The number 63 has the prime factorization 3, 3, and 7, and it contains one of them (3) as a substring. In contrast, the number 4...

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Sum along each diagonal of a matrix
Write a routine that returns the sums along the diagonals of a given matrix, A, where the first diagonal is the bottom left corn...

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2x2 binning of a large sparse matrix
Consider the 20000 x 20000 sparse matrix, A=round(sprand(2e4,2e4,1/1e4*100)*1000); The task is to divide this matrix into 2x...

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Throwing Dice - Will You Be Eaten By The Dragon?
You and a dragon have agreed to let dice rolls determine whether it eats you or not. The dragon will roll a single die, of x si...

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List the partitions of an integer
Several Cody problems deal with partitions of an integer, or the ways an integer can be written as the sum of positive numbers—...

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Compute the dispersion coefficient
A contaminant dumped or spilled into a river will move downstream with the flow, but it will also spread in the flow direction b...

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Describe n from right to left
If you were to describe the number 46 from right to left, you could say “one 6, one 4”, or 1614. The number 8663 would be “one 3...

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Extend the digamma function to negative arguments
While solving one of Ramon Villamangca’s problems, I needed the value of , where is the digamma function. However, MATLAB’s fun...

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List Ormiston prime pairs
The numbers 1913 and 1931 form the first Ormiston prime pair. The numbers are consecutive primes, and they are anagrams of each ...

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Moyenne pondérée
Ecrire une fonction qui prend en entrée un vecteur P et un vecteur V et calcule la moyenne pondérée MP des élements vi d'un vec...

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Special matrix
Make a square matrix with this shape. For n=4 M = 1 1 0 0 1 0 1 0 0 1 0 ...

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Explore the twin prime Goldbach conjecture
The Goldbach conjecture says that every positive even integer greater than 2 can be expressed as the sum of two prime numbers in...

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Write a code to implement Euler's method to integrate a simple function
Euler's method approximates the solution to a differential equation as where . The challenge is to write a code that can take...

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Given the mass and stiffness of an undamped SDOF system, find the natural frequency and the natural period of vibration
Problem Statement Given the mass and stiffness of an undamped SDOF system, find the system's natural frequency in both Hz and...

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