Solved

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). ...

10 months ago

Solved

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...

10 months ago

Solved

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...

10 months ago

Solved

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...

10 months ago

Solved

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...

10 months ago

Solved

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 ...

10 months ago

Solved

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...

10 months ago

Solved

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

10 months ago

Solved

Solve a nonlinear difference equation

10 months ago

Solved

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...

10 months ago

Solved

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 ...

10 months ago

Solved

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

10 months ago

Solved

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...

10 months ago

Solved

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 ...

10 months ago

Solved

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...

10 months ago

Solved

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-...

10 months ago

Solved

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 ...

10 months ago

Solved

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...

10 months ago

Solved

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...

10 months ago

Solved

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

10 months ago

Solved

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 ...

10 months ago

Solved

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...

10 months ago

Solved

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: ...

10 months ago

Solved

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

10 months ago

Solved

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...

10 months ago

Solved

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...

10 months ago

Solved

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...

10 months ago

Solved

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

10 months ago

Solved

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...

10 months ago

Solved

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 ...

10 months ago