Solved

Cummulative Count
Given a row vector of integers (with repeating values) , create an array that is the cumulative count of the unique values - ...

11 months ago

Problem

Grimm's Conjecture
Grimm's conjecture states that to each element of a set of consecutive composite numbers, one can assign a unique prime number t...

11 months ago | 0 | 5 solvers

Solved

Search for seesaw primes
Cody Problem 60958 introduced seesaw numbers. A number is a seesaw number if the next smaller numbers can be placed on a seesa...

12 months ago

Problem

Find the Prime Factors and Divisors of a Number
Given a positive integer n, find its prime factors as well as all of its divisors. Example: n=12 has prime factors [2,2,3] and ...

12 months ago | 0 | 10 solvers

Solved

Compute the nth term from the Sieve of Flavius Josephus

12 months ago

Solved

Count the primes in Collatz sequences
Several Cody problems (21, 69, 42937, 44448, 44784, 52422) involve Collatz sequences. These start with a seed . If is odd, the ...

12 months ago

Solved

Find pairs of primes with the same digit sum

12 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 ...

12 months ago

Solved

List the first of three consecutive square-free numbers
The numbers 13, 14, and 15 are consecutive, of course, but they also share the property of being square-free. That is, each numb...

12 months ago

Solved

List Proth primes

12 months ago

Solved

Summing Digits within Text
Given a string with text and digits, add all the numbers together. Examples: Input str = '4 and 20 blackbirds baked in a...

12 months ago

Solved

Determine whether a number is a Blum integer
A Blum integer is a semiprime—that is, the product of two distinct primes—whose factors have the form for some integer . The nu...

12 months ago

Solved

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 ...

12 months ago

Solved

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...

12 months ago

Solved

List numbers that cannot be expressed as the sum of two primes
The Goldbach conjecture claims that even numbers greater than 2 can be expressed as the sum of two prime numbers. What about the...

1 year ago

Solved

List primes of the form xy+z
Consider three consecutive integers , , and . When is the number prime? For example, if or , then the results are 17 and 37, ...

1 year ago

Solved

Compute the number of squares a knight can reach after n moves
Several Cody problems involve knights from chess. They have asked players to find a knight’s tour in a matrix (CP 96), determine...

1 year ago

Solved

Express numbers as the sum of a prime, a square, and a cube
While traveling on an interstate highway, I noticed a sign that gave distances to three places. The distances were 3, 8, and 9 m...

1 year ago

Solved

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

1 year ago

Solved

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...

1 year ago

Solved

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, ...

1 year ago

Solved

Create a vector whose elements depend on the previous element
The idea is to create a vector A whose elements depend on the previous element : *A(i+1) = 2*A(i)+1* *2 Inputs*: - A : The...

1 year ago

Solved

Check Euler's characteristic on regular polyhedra
Problem statement Given the number of vertices and the number of faces of a given regular polyhedron, compute the number of its...

1 year ago

Solved

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...

1 year ago

Solved

List mean-of-2 primes
The prime number 53 is the average of the first prime before it (47) and the first prime after it (59), and the prime number 11 ...

1 year ago

Solved

List balanced primes
A balanced prime of order is one that equals the average of the primes before it and the primes after it. For example, 79 is ...

1 year ago

Solved

Project Euler: Problem 7, Nth prime
By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13. What is the Nth prime numb...

1 year ago

Solved

Prime factor digits
Consider the following number system. Calculate the prime factorization for each number n, then represent the prime factors in a...

1 year ago

Solved

Check p² = 24k + 1, p > 3, the 'golden prime squares' equation
Historical context In december 2023, I / Nicolas Douillet was working on prime squares properties and I found* the formula : ...

1 year ago

Solved

List the twin prime couples
Problem statement The twin prime couples (p,p') are the ones such that p' = p + 2. For a given integer n > 1, list the twin p...

1 year ago