Questions tagged [factorial]
Involving calculation or other usage of factorials
19
questions
34
votes
35answers
5k views
Repeated! Factorials!
Not to be confused with Find the factorial!
Introduction
The factorial of an integer n can be calculated by
$$n!=n\times(n-1)\times(n-2)\times(...)\times2\times1$$...
32
votes
21answers
2k views
A Note on N!
J. E. Maxfield proved following theorem (see DOI: 10.2307/2688966):
If \$A\$ is any positive integer having \$m\$ digits, there exists a positive integer \$N\$ such that the first \$m\$ digits of \$...
1
vote
3answers
342 views
Finding Factorials with Gamma [duplicate]
Introduction
We know that the factorial notation is valid for all natural numbers. However, Euler had extended it for all positive real numbers, as well as for complex numbers by defining a function, ...
16
votes
5answers
868 views
Factoring factorials
Today in my statistics class, I found that some factorials can be simplified when multiplied together! For example: 5! * 3! = 5! *3*2 = 5! *6 = 6!
Your job:
Given ...
17
votes
21answers
2k views
Additional facts!
In mathematics, the factorial, shortened "fact" of a non-negative integer n, denoted by n!, is the product of all positive integers less than or equal to n. For example, 5! is 1 * 2 * 3 * 4 * 5 = 120
...
11
votes
7answers
683 views
Do two numbers contain unique factorials?
Break two numbers up into their factorials; if they share any, return a falsey value. Otherwise, return a truthy value. (inspired by this recent question)
In other words, write each input number as ...
33
votes
24answers
3k views
Factorials and never ending cycles!
As you may know it, the factorial of a positive integer n is the product of all the positive integers which are equal or smaller to ...
175
votes
47answers
28k views
Mathematics is fact. Programming is not
In mathematics an exclamation mark ! often means factorial and it comes after the argument.
In programming an exclamation mark !...
25
votes
34answers
3k views
Big numbers: Ultrafactorials
This question was reworked, please re-read it.
Ultrafactorials
The ultrafactorials are a sequence of numbers which can be generated using the following function:
...
25
votes
49answers
3k views
Factorial digit sum
The challenge is to calculate the digit sum of the factorial of a number.
Example
Input: 10
Output: 27
10! = 10 × 9 × ... × 3 × 2 × 1 = 3628800,
and the sum of ...
39
votes
29answers
3k views
Pseudofactorial
There is a rather curious number which shows up sometimes in math problems or riddles. The pseudofactorial(N) is the least (i.e. lowest) common multiple of the numbers 1 through N; in other words, it'...
35
votes
50answers
5k views
Zeroes at the end of a factorial
Write a program or function that finds the number of zeroes at the end of n! in base 10, where n is an input number (in any ...
22
votes
12answers
1k views
Last Nonzero Digits of a Factorial in Base
You should write a program or function which given three positive integers n b k as input outputs or returns the last k digits ...
1
vote
4answers
706 views
Memory is Expensive [closed]
You are a robot. You are stranded in a small cage with weird humans wearing weird suits looking at you. Your solar panel is malfunctioning, and your energy is running out. On the wall there is a ...
12
votes
16answers
6k views
How much can you quickly multiply?
With the recent Python bashing, here's an attempt to show Python's strengths.
Your challenge is to write a program that calculates the factorial of as high a number ...
30
votes
9answers
3k views
Calculate the inverse of factorial
Write the shortest code that will take any real number greater than 1 as input and will output its positive inverse factorial. In other words, it answers the question "what number factorial is equal ...
-15
votes
19answers
9k views
Calculate the factorial of a number without using recursion or loops [closed]
The goal of this code golf is to create a program that calculates the factorial of a positive number, without using recursion or loops.
The rules:
Your program should prompt for input. This input ...
22
votes
28answers
3k views
Last non-zero digit of n!
Given an integer 1 ≤ N ≤ 1,000,000 as input, output the last non-zero digit of N!, where ! is the factorial (the product of all numbers from 1 to N, inclusive). This is OEIS sequence A008904.
Your ...
75
votes
180answers
15k views
Find the Factorial!
Create the shortest program or function that finds the factorial of a non-negative integer.
The factorial, represented with ! is defined as such
$$n!:=\begin{...
