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First Poster
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Stars and Bars variation
patrickzheng   9
N Aug 15, 2024 by patrickzheng
So let’s say we want to find how many ways we can put 20 balls into 7 boxes, where the boxes and balls are indistinguishable. For this, we can just use stars and bars, which would be 26choose6. But what would be the answer if the boxes are different? Should I multiply by 6! or 7 factorial? Thanks!
9 replies
patrickzheng
Aug 12, 2024
patrickzheng
Aug 15, 2024
F!A!C! + T!O!R! + I!A!L!
FliX0onbo   10
N Jun 8, 2024 by FliX0onbo
Compute $155 * \frac{13!12!11!10! + 14!12!11!10! + 14!13!11!10! + 14!13!12!10!}{14!13!12!11! + 13!12!11!10!}$ (Express your answer as a common fraction.)

Edit 1: Multiplication by $10!$ for cleaner answer
10 replies
FliX0onbo
Jun 1, 2024
FliX0onbo
Jun 8, 2024
Factorial www
LostDreams   5
N May 22, 2024 by ChaitraliKA
yo guys i am stuck so a factorial is n! = n(n-1)...(1) how do i know that it counts all cases for the possible rearrangements for n elements given all distinct?
5 replies
LostDreams
May 21, 2024
ChaitraliKA
May 22, 2024
sum of factorials
kb_alcumus   9
N Feb 4, 2024 by RedChameleon
is there a way to find the sum of factorials without calculating each one
like is there a way to compute 1! + 2! + 3! + 4! + ... + n!
9 replies
kb_alcumus
Feb 4, 2024
RedChameleon
Feb 4, 2024
infinity factorial
Gentlefrog   12
N Aug 21, 2023 by Mr.BigBrain_AOPS
Theoretically, ∞ factorial is ∞ × (∞ – 1)! = ∞ × ∞! = ∞ × ∞ × (∞ – 1)! = ∞^2 × ∞!

Theoretically, you can repeat this process an infinite amount of times meaning that ∞!=∞^∞

What do you guys think of this logic?
12 replies
Gentlefrog
Aug 21, 2023
Mr.BigBrain_AOPS
Aug 21, 2023
k 0 factional is confusing me
Gentlefrog   5
N Aug 17, 2023 by Gentlefrog
n! = n × (n – 1) × (n – 2) × … × 1

That is the formula for factorials. I heard that 0 factorial is 1. However if we plug 0 in for n we get 0 times something, which must be 0. So how is 0! 1? I think 0 is the most confusing number because it breaks math in so many ways. Maybe ancient mathematicians were on to something when they didn’t think 0 was an actual number. Lol but seriously why on earth is 0! equal to 1?
5 replies
Gentlefrog
Aug 17, 2023
Gentlefrog
Aug 17, 2023
Is it possible to make 16 with only 1 four?
only1unicorn   123
N Jul 21, 2023 by juicetin.kim
Any operation is allowed. I want to see if it is possible.
Rules are though:
- The only number you can have is four. Only 1 four is allowed.
- You can use any operation you'd like. (you can use mods, factorials, floors, anything!)
123 replies
only1unicorn
Jul 4, 2023
juicetin.kim
Jul 21, 2023
Factorial
YaoAOPS   26
N Jun 20, 2023 by aidan0626
Compute the first few digits of $7286!$
26 replies
YaoAOPS
Jun 14, 2023
aidan0626
Jun 20, 2023
k 9 0 Factorial (0!)
AbhayAttarde01   60
N May 15, 2023 by Danielthepenguin
So I've been pondering about the actual amount of $0!$, and some people think its $0$, while some people say its $1.$ Can someone tell me why their answer is $0$ or $1$?
60 replies
AbhayAttarde01
Apr 27, 2023
Danielthepenguin
May 15, 2023
Write formulas using sums?
Flamable_Water_42   1
N May 4, 2023 by peelybonehead
How would someone write factorials and $\dbinom{n}{r}$ using product notation?
1 reply
Flamable_Water_42
May 4, 2023
peelybonehead
May 4, 2023
a