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Count the ways to draw non-intersecting chords between points on a circle
There are 9 ways to draw non-intersecting chords between four points on the perimeter of a circle (including no chords at all). ...

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Sum the elements in rows of the Levine triangle
The Levine triangle starts as follows: Row 0: 2 Row 1: 1 1 Row 2: 1 2 Row 3: 1 1 2 To construct each row, r...

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List the dopey numbers
If vile numbers have binary representations that end with an even number of zeros (even vile), then numbers with binary represe...

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Fill a rectangle with 1x1 and 2x2 tiles
A 3x2 rectangle can be filled with 1x1 and 2x2 tiles in three ways: The colors merely distinguish the sizes of the tiles. A 3...

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List the vile numbers
Evil numbers, the subject of Cody Problem 2733 have an even number of ones in their binary representations, whereas odious numbe...

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Find the nth nude number
The number 672 is a nude number because it openly displays three of its divisors: 6, 7, and 2. In other words, a nude number is ...

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Determine whether a number is a fibodiv number
The number 14 is a fibodiv number because you can divide it into 1 and 4, use those numbers as the seeds for a Fibonacci sequenc...

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Optimum Egyptian Fractions
Following problem was inspired by <http://www.mathworks.com/matlabcentral/cody/problems/2126-split-bread-like-the-pharaohs-egypt...

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Solve a nonlinear difference equation

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Count unique orderings of vertices of a polygon
Cody Problem 2671 asks us to determine whether four points can be the corners of a rectangle. The points are not necessarily inp...

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Identify Ruth-Aaron numbers
After Hank Aaron hit his 715th home run and passed Babe Ruth’s total of 714, Carl Pomerance noticed that the union of the prime ...

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Prime Ladders
A <http://en.wikipedia.org/wiki/Word_ladder word ladder> transforms one word to another by means of single-letter mutations. So ...

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Pandigital number n°3 (Inspired by Project Euler 32)
After Problem 2319 and 2320. An n-digit number is pandigital if it makes use of all the digits 1 to n exactly ONCE. For examp...

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Find all vampire fangs
A vampire number is a number v that is the product of two numbers x and y such that the following conditions are satisfied: at ...

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Make a Pandiagonal Prime Magic Square: 11 x 11
This Fun with Primes Challenge is to create a Pandiagonal Prime Magic Square of size 11x11 given eleven APk sequences with 10 co...

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Pandigital number n°2 (Inspired by Project Euler 32)
After Problem 2319. An n-digit number is pandigital if it makes use of all the digits 1 to n exactly ONCE. For example, the 5-...

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Fangs of a vampire number
A vampire number is a number v that is the product of two numbers x and y such that the following conditions are satisfied: at ...

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Pandigital number n°1 (Inspired by Project Euler 32)
A little warm-up to begin... An n-digit number is pandigital if it makes use of all the digits 1 to n exactly ONCE. For ex...

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Pandigital Factors (Based on Euler 491)
A Pandigital Number is a number containing all of the digits from 0-9 inclusive, with the added stipulation that it does not hav...

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is the number happy?
test is a given integer number is Happy of not? answer 1 if yes or 0 is no

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Pandiagonal Prime Magic Square Verification
Verify if an NxN matrix is a Pandiagonal Prime Magic Square. Required properties: 1) N^2 prime values ( No repeats, 1 ...

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Dudeney Numbers: Numbers which are the cube of their decimal sum
From Wikipedia: _A Dudeney number is a positive integer that is a perfect cube such that the sum of its decimal digits is equa...

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Factorions: Numbers that equal the sum of the factorials of their digits
From Wikipedia: _A factorion is a natural number that equals the sum of the factorials of its decimal digits_ For example: ...

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Happy 2013...
Happy 2013, everyone! An interesting tidbit about 2013 is that it is the first year since 1987 to contain four different digits...

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Lychrel Number Test (Inspired by Project Euler Problem 55)
The task for this problem is to create a function that takes a number _n_ and tests if it might be a Lychrel number. This is, re...

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Largest Twin Primes
<http://en.wikipedia.org/wiki/Twin_prime Twin primes> are primes p1, p2 = p1 + 2 such that both p1 and p2 are prime numbers. Giv...

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Mersenne Primes
A Mersenne prime is a prime number of the form M = 2^p - 1, where p is another prime number. For example, 31 is a Mersenne prim...

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Champernowne Constant
The <http://en.wikipedia.org/wiki/Champernowne_constant Champernowne constant> is a real number whose digits in decimal represen...

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Numbers with prime factors 2, 3 and 5.
Make a function which takes one positive integer n and returns a matrix with the numbers of the form (2^i)*(3^j)*(5^k) which are...

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Project Euler: Problem 9, Pythagorean numbers
A Pythagorean triplet is a set of three natural numbers, a b c, for which, a^2 + b^2 = c^2 For example, 3^2 + 4^2 = 9 + 16 ...

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