5 ms·
Can someone ELI5 this post?
by jakelazaroff 4y ago
Can someone ELI5 this post?
- loeg 4y ago
- layer8 4y agoR49081 is the natural number consisting of 49081 “1” digits in decimal base, or (10^49081 - 1)/9. This number has now been proven to be a prime number, using some number-crunching algorithm. Somebody else will have to ELI5 that algorithm.
- krasin 4y agoEdit: the OP is correct, I was confused by the forum name, as I thought it was about Mersenne primes, but this is about Repunit primes. Original response: Almost correct, but it's 2^49081-1, not (10^49081-1)/9. And there's no division by 9 at all. https://en.wikipedia.org/wiki/Mersenne_prime https://en.wikipedia.org/wiki/Mersenne_prime
- layer8 4y agohttps://primes.utm.edu/top20/page.php?id=57 https://primes.utm.edu/top20/page.php?id=57, linked in the article, begs to differ.
- krasin 4y agoThank you! You're right, this is not about a Mersenne prime, but about Repunit prime. Sorry about that!
- googlryas 4y agoNo, this is just on the mersenne prime forum. If you read [1] from the link it tells you OP is right.
- happytoexplain 4y agoI think the parent is right. This seems to be a decimal repunit, not binary. I can't find a positive reference, though.
- loeg 4y agoI don't think any of you have met five year olds.
- quickthrower2 4y agoThis would be totally inexplicable to 5 year olds, except the odd genius. But we took it as intended i.e. "can someone explain this in a simpler way, defining terms like "R""
- saghm 4y agoIdk, I'd try something like "you know how the number one is a single 1 digit, and eleven is two 1 digits? If you have 49081 one digits, that number is really big! We don't even have a word for it, so we call it R49081. Some very smart people worked really hard and found out that number is prime!", after explaining what "prime" is (which I think would be a lot easier).
- whatshisface 4y agoELI5 posts are reduced to fantasy by the attention span of actual 5 year olds if nothing else. :-)
- saghm 4y agoNot all five year olds are the same, and the premise is that a 5 year old who wanted to know asked.
- whatshisface 4y agoMost young children want to know everything, it's the attention span to make it through an explanation of prime numbers that would be rare.
- quickthrower2 4y ago
- mastazi 4y agoI knew nothing about Repunit numbers until a few minutes ago. So far, the most interesting bit for me was that: > As of March 2022, the largest known prime number 282,589,933 − 1, the largest probable prime R8177207 and the largest elliptic curve primality prime R49081 are all repunits. Source https://en.wikipedia.org/wiki/Repunit https://en.wikipedia.org/wiki/Repunit
- deleted 4y ago[deleted]
- romellem 4y agoSo this number is prime? Cool. const R49081 = BigInt('1'.repeat(49081));
- pxmpxm 4y agoIs there a practical applicate for this, or is that more of a large pizza problem? https://pbs.twimg.com/media/CHtVwLXXAAAeKR6?format=jpg&name=small https://pbs.twimg.com/media/CHtVwLXXAAAeKR6?format=jpg&name=...
- kristopolous 4y agoApparently it's just that number of 1s followed by each other as a number. https://en.wikipedia.org/wiki/Repunit https://en.wikipedia.org/wiki/Repunit It's part of "recreational mathematics" which solves a longstanding question I've had after finding out about a "special" set of numbers that make me think "What the hell was that?" Basically the question was "Why can't I just come up with any dumb rule I want? Like the number of letters in the number being equal to the number of digits in the base ten representation or some other noise like the number of toothpicks required to represent it in decimal and then do some wacky proofs regarding "toothpick count"?" Apparently the answer is "well you can!" Alright then. There exists a non-serious branch of math.
- defrost 4y ago> There exists a non-serious branch of math. This remains an unproven conjecture that many hope to be true . . .
- kristopolous 4y agowell this gives me hope that the solemn attitudes surrounding recreational mathematics is just math kayfabe and I'm not actually nuts. Although I will concede those are not mutually exclusive claims.
- defrost 4y agoGeorge Conway and others have at times lamented that whenever somebody arrives at something sufficiently complex to be intriguing and no apparent real world application ... military gentrification follows within a decade.
- schoen 4y ago> Like the number of letters in the number being equal to the number of digits in the base ten representation You might not be happy that someone investigated this because you apparently made up this example in order to make fun of this kind of question, but I looked into this a little bit and it's more subtle than I first thought. The typical random integer small enough to have a well-defined English name (following Guy and Conway's prefixes at https://en.wikipedia.org/wiki/Names_of_large_numbers#Extensions_of_the_standard_dictionary_numbers https://en.wikipedia.org/wiki/Names_of_large_numbers#Extensi... which will go up to 10³⁰⁰⁰-1) has a significantly longer English name than its decimal expansion. E.g. if we take fifty random digits like 96689907044105050355231217362382284051155144740067 the name of this number is "ninetysixquindecillionsixhundredeightyninequattuordecillionninehundredseventredecillionfortyfourduodecilliononehundredfiveundecillionfiftydecillionthreehundredfiftyfivenonilliontwohundredthirtyoneoctilliontwohundredseventeenseptillionthreehundredsixtytwosextillionthreehundredeightytwoquintilliontwohundredeightyfourquadrillionfiftyonetrilliononehundredfiftyfivebilliononehundredfortyfourmillionsevenhundredfortythousandsixtyseven" or 430 letters, while the number is written with only 50 digits. For small numbers, the closest approach between the lengths of the two is 10 (len("ten") == 3, len("10") == 2). And the typical word length grows faster than the digit length. But the lengths do cross over many times up in the illions, as the illion terminology is unusually short compared to the size of the number described. Specifically, the smallest integer where this occurs is 1,000,000,000, where len("onebillion") == len("1000000000"). That's the smallest member of your set. There are other examples such as 10¹³+1, 10¹³+2, 10¹³+6: len("tentrillionone") == len("tentrilliontwo") == len("tentrillionsix") == len("10000000000001") And there are many more further out into the illions. For any example in which "one", "two", or "six" appears in the name of a number, any of the others can be substituted and the property will still hold. Likewise for "four"-"five"-"nine" and "three"-"seven"-"eight".
- softdevca 4y agoI may have misconstrued that ELI5 was snark for "elide", in the same vein as I18N or A11Y. Present me wishes I could explain Explain ELI5 Like I'm 5 to my past self.
- charles_f 4y agoBiiiiiig number with only 1s is magical and doesn't fear the other numbers to cut it in bits and pieces, which is awesome and exciting because it's fun. Daddy only hopes it's got a solid self estime and doesn't hang out too much in those shady unary parts of the universe