Questions tagged [factoring]

This tag describes challenges related to factoring numbers and polynomials. Not related to the Factor esoteric programming language.

4
votes
0answers
105 views

Fastest way to iterate over sublattice of discrete lattice

I need to construct a functor that iterates over the linear representation of a sub-lattice of size \$d_x,d_y,d_z,d_q\$ embedded in a lattice of size \$n_x,n_y,n_z,n_q\$. The sub-lattice corner is ...
2
votes
1answer
174 views

Find all diagonal counts in only one direction [closed]

If I need to get the number of diagonal squares in all directions: I do the following formula 2 N − 2 − |x − y| − |x + y − N − 1| The above example has 13 and ...
28
votes
45answers
8k views

Am I not good enough for you?

Background: The current Perfect Numbers challenge is rather flawed and complicated, since it asks you to output in a complex format involving the factors of the number. This is a purely decision-...
15
votes
11answers
873 views

Generate some rough numbers

Background A number n can be described as B-rough if all of the prime factors of n strictly ...
19
votes
34answers
2k views

Find the Squarish Root

Write code that when given a positive number \$x\$ as input, outputs the largest positive divisor of \$x\$ less than or equal to the square root of \$x\$. In other words find the largest \$n > 0\$ ...
15
votes
10answers
1k views

Prime Factor Encoding

How the encoding works Given a list of bits: Hold a prime (starting with 2) Have a list For each bit in the input If it's the same as the previous bit, add the ...
31
votes
10answers
1k views

Find the dot product of Rationals

I was at a friend's house for dinner and they suggested the idea of a "Prime-factor vector space". In this space the positive integers are expressed as a vector such that the nth element in the ...
16
votes
7answers
616 views

Queue Our Decomposition

In this challenge I will ask you to find a QR decomposition of a square matrix. The QR decomposition of matrix A is two Matrices Q and R such that A = QR. In particular we are looking for Q to be an ...
11
votes
5answers
296 views

Primes ’n’ Digits

This has no practical purpose but it could be fun to golf. Challenge Given a number n, Count the amount of each digit in n and add 1 to each count Take the prime factorization of n Count the amount ...
21
votes
5answers
765 views

Is my number Unique

In this challenge we learned a way to encode every positive integer using factor trees. Here is how it works: The empty string has value of 1. (S) where ...
21
votes
21answers
2k views

Determine Superabundance

A superabundant number is an integer n that sets a new upper bound for its ratio with the divisor sum function σ. In other words, n is superabundant if and only if, for all positive integers x ...
13
votes
7answers
364 views

Encode Factor Trees [duplicate]

I once saw on the xkcd fora a format for expressing numbers in an odd way. In this "factor tree" format: The empty string is 1. Concatenation represents multiplication. A number n enclosed in ...
22
votes
28answers
2k views

Largest Prime Exponents

Given an integer n >= 2, output the largest exponent in its prime factorization. This is OEIS sequence A051903. Example Let ...
19
votes
45answers
2k views

Find the sum of the divisors of N

Write a program that displays on the screen the sum of the divisors of a number (1 ≤ N ≤ 100) entered by the user in the range of 1 to N. This is OEIS A000203. Examples: Input: 7 ...
33
votes
11answers
2k views

Encode an integer

Given positive integer n > 2. We convert it to an array as follows: If it is equal to 2 return an empty array Otherwise ...
12
votes
7answers
507 views

Number of sums of factors

Given a positive integer n > 1 determine how many numbers can be made by adding integers greater than 1 whose product is n. For example if n = 24 we can express n as a product in the following ways <...
7
votes
7answers
452 views

Composite Factorization

This is similar to prime factorization, where you find the smallest prime factors of a number (i.e. 8 = 2 x 2 x 2). But this time, you are to return an array/list of the smallest composite factors of ...
27
votes
33answers
2k views

Calculate the prime factors

We had a prime factorization challenge a while ago, but that challenge is nearly six years old and barely meets our current requirements, so I believe it's time for a new one. Challenge Write a ...
34
votes
14answers
1k views

Generate n-ary numbers

A secondary number is a positive integer whose prime factors (without multiplicity) are all less than or equal to its square root. 4 is a secondary number, because ...
21
votes
10answers
1k views

Prime factors buddies

Given an integer N > 1, output all other numbers which prime decompositions have the same digits as the prime decomposition of ...
14
votes
13answers
739 views

Palindromic Prime Factors

Palindromic prime problems are pretty common, but that's not what this question is about. In this challenge, the number doesn't have to be a palindrome, its prime factors do. Task Your code has to ...
27
votes
18answers
1k views

Sums of prime factors

2013 has the prime factorization 3*11*61. 2014 has the prime factorization 2*19*53. An interesting property regarding these ...
20
votes
9answers
966 views

Novel Prime Factors of Repunits

The Background Folks were talking prime factorization in chat and we found ourselves talking about repunits. Repunits are a subset of the numbers known as repdigits, which are numbers consisting of ...
22
votes
3answers
2k views

Factoring a 64-bit integer

Write a GOLF assembly program that reads an integer from stdin (followed by a trailing newline), and outputs its prime factors seperated by newlines, followed by a trailing newline on stdout. The ...
8
votes
3answers
1k views

List prime-factorized natural numbers up to N in ascending order

For a given n list prime factorization of all natural numbers between 1 and n in ascending ...
22
votes
23answers
3k views

Find the prime factors

In this task, you have to write a program, that computes the prime factors of a number. The input is a natural number 1 < n < 2^32. The output is a list of the prime factors of the number in the ...