Double Factorials

[@TheOrganicChemistryTutor]

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[@abbeyrhapsody3205]

I didn't know there was a thing called "double factorial" so far! Thanks so much! You deserve more and more!

[@Lionfish5656]

Me too. Pretty interesting. I came here looking to get some review for hyperbolic functions for a math related project to take a math conference this Spring. Factorials are apparently rather vital in hyperbolic functions it seems.

[@LanoMusambazi-sr6mx]

Same here. I've just learned this today.

[@user-vq5gv1vg3w]

I graduated already, but feel I've learned a bit better under my personal studies(Math). No deadlines or pressures, thank you.

[@nickoemmanuelvillacruz3090]

Never learned this in elem and high school

[@juicewrld822]

@Nicko Emmanuel Villacruz, Yeah it all depends how… 🤔 *I think it’s either early or later* you start school?

[@_Just_Another_Guy]

​@@juicewrld822I never learned about Double Factorials or Iterative Factorials in elementary or highschool either but these topics seem like it can be taught as early as junior year of highschool. The concepts aren't that difficult to grasp. I was already being taught introductory calculus in junior year which is way more complex than Double Factorials and Iterative Factorials.

[@louf7178]

*nor

[@sumportuguesedude2605]

You aren't supposed to even learn factorials in elementary

[@MosMoses-h8t]

Are you in eden Paradise 😢

[@georgesadler7830]

MR. Organic Chemistry Tutor, thank you for a great video on Double Factorials.

[@randomdoode]

Mac n cheese

[@Zersara]

Never knew single factorials existed!! School never teach us but this is really interesting ~ thank you for teaching us 💗

[@dileep_j203]

I also thought 5!! =120! 😀😁

[@ilikeanimals5015]

Ill punch you

[@dileep_j203]

@@ilikeanimals5015 😁

[@happykumarray8638]

15

[@VCOTABFONDD]

You make Comic Sans look good 😂😂

[@coolmanchu275]

Can you please make a video on graphing calculators?

[@_Just_Another_Guy]

I never learned about Double Factorials or Iterative Factorials in elementary or highschool either but these topics seem like it can be taught as early as junior year of highschool. The concepts aren't that difficult to grasp. I was already being taught introductory calculus in junior year which is way more complex than Double Factorials and Iterative Factorials.

[@dougdavis8986]

What is the functional use of a double factorial? Is there a triple factorial? A septuple factorial?

[@CrystallizeOfficial666]

There could be an infinite amount of factorials, such as 4!!!, 7!!!!, (if you wanted) there could even be 9999!!!!!!!!!!!!!!!!

[@jamsty8225]

Your Videos are really helpful 😄

[@irichardoteng1515]

thanks for teaching me about this :) this vid helped me alot with my upcoming test

[@LanoMusambazi-sr6mx]

Thank you sir. I didn't know this double and iterated factorial.

[@MajaxPlop]

You can write double factorials using simple factorials if you take the even and odd cases apart. For the even case, (2n)!! = 2^n × n! We can show it using this : 2 × 4 × ... × (2n - 2) × 2n = 2 × 1 × 2 × 2 × ... × 2 × (n - 1) × 2 × n = 2^n × 1 × 2 × ... × n = 2^n × n! The odd case is a bit more difficult, we have (2n + 1)!! = (2n + 1)! / (2^n × n!) To show this, we write : (2n + 1)! = 1 × 2 × 3 × ... × 2n × (2n + 1) = 1 × 3 × ... × (2n + 1) × 2 × 4 × ... × 2n = (2n + 1)!! × (2n)!! Therefore, we have (2n + 1)!! = (2n + 1)! / (2n)!!, or (2n + 1)!! = (2n + 1)! / (2^n × n!)

[@6710lili]

Explain why 5!!= 5×3×1. From what, do you deducted this ? What about 5 !!!? Or 5!!!!.....or 5n! (5!!!!!!!!.....n)?

[@nosir1479]

God blessed Earth with your happening and graciousness

[@jazzabighits4473]

What are double factorials used for?

[@henryfayol6667]

I guess you got to find out pls 🤔🤔🤔🇬🇭

[@jazzabighits4473]

@@henryfayol6667 I never got an answer. A factorial is looking at how many ways a a set or group can be arranged, i have no clue what a double factorial denotes

[@khypichkholine4257]

This made my day

[@tirthankarsingh8776]

Thanks a lot This is something new I never saw .👍👍👍👍👍👍✌️✌️✌️✌️

[@s.4155]

This is such an interesting video!

[@reinlepiku445]

All my calculators (CAS and non CAS) give different answers than in this video. For example 3! = 720 The TI-86 and HP Prime can also calculate the double factorial of a number expressed as a decimal fraction. For example 3.3!! = 262289.062411 Also GOOGLE CALCULATOR on PC desktop can do it. (Ti-89, TI-Nspire CX CAS cannot do this!)

[@henryfayol6667]

Waow! Double factorial !!. Then what of triple factorial !!!😆🤔🤔eeeih!

[@2025akashverma]

To give extra knowledge...... thanks alot

[@henrymusonda2734]

Wow wow thank you ❤️💯🙏 I've learned

[@VICS_SFTM2010]

Using odd and even numbers in double factorials

[@ვ3ვ3ვ]

(googolplex!)! Is it comperable with graham's number?

[@StevenTorrey]

When in practical math would a double or integrated factorial crop up? Or for that matter any factorial?

[@Che1ito]

A factorial gives you the amount of orders of choices you have when you have a sample of choices. For example, if you have 5 toys and want to know how many different orders there are of choices, you can take 5! and know that there are 120 different outcomes. (ABCDE, ACDEB, ADCEB,....., etc.) I'm not sure on a double or integrated factorials.

[@NeelTigers]

Students: Hmm..how can there be two factorials? Legends: wait..why’s this dude so excited about 5

[@banvibol7990]

Thanks teacher

[@SumanRoy.official]

Calculator got math error when calculating double factorial LOL 😁

[@Steshan]

Because the calculator probably tried to calculate 5 factorial factorial which is equal to 120!

[@henryfayol6667]

😂😂😂😂. Even scientific calculator has a limit 😮😮😮😅😅

[@someshchaudhary3045]

Thank you sir😋

[@principleinstitutetelugu8274]

Ur awesome brother

[@kon8024]

Do eigen values and eigenvectors

[@acedluffy5]

This is a thing?

[@jeemonjose]

Any reason why the double factorial is that specific way? Like you multiply every alternate number. And similarly, is a triple factorial something you get when you multiply every third number?

[@antimatter31]

You’re a saviour you know that?

[@iftikharalikhan4303]

Well done.

[@olawunistephen9778]

Thank you so much.....pls I need your help....for a video on LENS MAKER FORMULA... calculations and explanations ...pls

[@dimuthupraboda]

Thank you. Love from srilanka. I want to know. when I type double Factorials in a cal. why I get a factorial's factorial. ex :- 3!! -> 720 It's like :- 3!! :- 6! :- 720

[@guliyevshahriyar]

thank you

[@NormieDead]

my calculator is giving 720 for 3!!

[@henryfayol6667]

Me to some conditions do not hold 😂

[@Xnoob545]

That looks like a renamed wither's health bar

[@barnobarno5403]

Man you're awesome

[@User_forbidden]

1:50 Short version.

[@allmight801]

now integrate double factorial

[@IcefisherTenacity]

If I was formulating this operation I would have prioritized not making it nearly indistinguishable from “a factorial of a factorial”. Yes you can just tell people that (4!)! Is not the same as 4!!, or you could have just made a new symbol.

[@kiwifruit_T]

Is triple factorial possible? Like 6!=18

[@RafaelBorgesRDB]

I wonder why is there a "n x 1" on factorials, if that's neutral.

[@smpblack23]

thanks

[@Taha-yd4gp]

Interesting!

[@jishanbhattacharya8021]

What would 0!! and 1!! be equivalent to?

[@_Just_Another_Guy]

To understand, first consider what the basic factorial n! means. It means how many possible ways a group of items can be arranged. For example, if we have 3 items: A B C then n=3. Let's find out how many ways to organize A B C in order: A B C A C B B A C B C A C A B C B A There are 6 different ways to organize a group of items A B C. Thus, 3 items can be written as _3!_ 3! = 1 × 2 × 3 3! = 6

[@_Just_Another_Guy]

Thus 0! and 1! Both equal to 1. For 0!, there are no possible arrangements other than one (which is "nothing"). So it's 1. For 1! there's only one possible arrangement of 1 item. And for the double factorials of 0!! and 1!! since there's only 1 possible arrangement, then the answer is also 1.

[@Igotyahomie]

​@@_Just_Another_Guywhat about 2!! ? Would be 2?

[@hannsahmed2352]

I had no idea about double factorial

[@chrishelbling3879]

Are we just making up nomenclature at this point?

[@steveross8364]

Number play, all very good and well but how about an example of a real world application or is it all just for theoretical bs guesswork?

[@UncFlinxy]

How about 0!! , is it possible?

[@eternity-308]

thatd just be 1

[@henryfayol6667]

It is one ☝️ 😢😅

[@kausikkar2587]

OMG!!! TODAY ONLY I CAME TO KNOW THAT SOMETHING CALLED 'DOUBLE FACTORIALS' EXISTS!!!! BTW, Love from India.🇮🇳🇮🇳 🇮🇳❤🇺🇸

[@sakumieika]

(10-n!)! what's the name of that, and how to calculate it, please, anyone?

[@_Just_Another_Guy]

It's looks like a form of iterative factorial. Let _n_ = 3 for example: (10 - 3!)! (10 - (3×2×1))! (10 - 6)! (4)! (4 × 3 × 2 × 1) 24 Note that n in this expression cannot be larger than 4 because it would result in a negative integer and factorials can only be done with positive integers.

[@sakumieika]

Oh! Thank you so much @@_Just_Another_Guy

[@focusonme7616]

I didn't learned this during my elem and highschool day,it only exist during our cal 2

[@Videowatcherhvgh]

What about triple factorial?

[@adilhameed8165]

May be if 7!!!= 7×4×1

[@randomvidson]

Me when I first saw double factorials: It'll just be final answer multiplied by two!😂. I got it all wrong🤦🏻

[@lilac624]

Okay double factorial is decreasing by 2...

[@yosufel4296]

What about 4!! ? 4*2*0=? I don't know!

[@icarokaue7334]

4*2.

[@ayushkumarjha9921]

(4!)! = (24)! = Very large number

[@bradical2577]

5!!

[@ayushkumarjha9921]

10!! = 10 × 8×6×4×2 = 3840

[@Victoria11337]

My college professor never taught me this 🙃

[@banvibol7990]

5!!!

[@banvibol7990]

Tutorials

[@icebluscorpion]

How would then the result look like I you have ((4!)!!)!🤔

[@sandstealers476]

Is there a such thing as an exponentiative divisional factorialized factorial? Like this: 5(^/!!) = 1! ^ 1!/2! ^ 1!/2!/3! ^ 1!/2!/3!/4! ^ 1!/2!/3!/4!/5!

[@dienzer9098]

Who else was thinking 5!! Would be 5! × 4! × 3! × 2! × 1! ?

[@farzeenferozeae9607]

Meee

[@mynlm]

Double factorial is n!! = (n!)!

[@Mobilesalahkar]

3!!=?, 2!!=?

[@tobiasbundgar7063]

wrong write 5 !! into google and u get 198 digit number

[@sarthakandsahilthakur4899]

Can't 8!! Be 8*6*4*2*0 = 0

[@rishavkru3274]

Factorials are only defined for natural numbers (and factors are natural numbers only)., And 0! doesn't mean 0*0=0, its different case proved by combination that 0! =1. So your 0 is not natural numbers and can't be multiplied as you stated

[@Jo_Es_Chess_Channel]

0 factorial is 1 so even if u do it it'll stay the same

[@Xnoob545]

U dont use 0

[@solidwaterslayer]

that was unexpected

[@GochiSiyan]

why is this useful?

[@fifaclips2501]

Good question

[@shashankkumarshah7279]

First time I saw...

[@stevenshrii]

N!!!?

[@raginglunatik8979]

Damn brackets always messing things up. Sometimes theyre not there but youre supposed to pretend they are. Sometimes its the other way around. I hate you math. Damn you. lol

[@mekdeskinfe5228]

Triple factorials tho.... _WHAT’S 6 x 3?_

[@Jojo_clowning]

No.

[@seenumca6533]

No means is there any way to find double factorial

[@iamaleczis]

7!=5040 10!!=38040 (4!)!=620448401733239439360000

[@kimanhchung8372]

Thanks