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Is This Prime?

isthisprime.com

11–20 of 139 posts

Re: Is This Prime?

#11

Is there a reason we're obsessed with primes beyond aesthetics? Why does this set of numbers garner all the headlines as opposed to some other arbitrary integer sequence like the Recamán numbers [0] ? If tomorrow someone discovered a closed-form equation for the nth prime, how would mathematics/the world change? [0] https://en.wikipedia.org/wiki/Recamán%27s_sequence

Your original link 404'd on me (you seem to have replaced it with a different one though). Here's the working Wikipedia link:

https://en.wikipedia.org/wiki/Recamán%27s_sequence

Re: Is This Prime?

#12

Is there a reason we're obsessed with primes beyond aesthetics? Why does this set of numbers garner all the headlines as opposed to some other arbitrary integer sequence like the Recamán numbers [0] ? If tomorrow someone discovered a closed-form equation for the nth prime, how would mathematics/the world change? [0] https://en.wikipedia.org/wiki/Recamán%27s_sequence

I'm not sure about a closed-form equation for the nth prime, but if integer factorization can be done in linear time then much of applied cryptography needs to be replaced.

Re: Is This Prime?

#13

Is there a reason we're obsessed with primes beyond aesthetics? Why does this set of numbers garner all the headlines as opposed to some other arbitrary integer sequence like the Recamán numbers [0] ? If tomorrow someone discovered a closed-form equation for the nth prime, how would mathematics/the world change? [0] https://en.wikipedia.org/wiki/Recamán%27s_sequence

The prime numbers are critical in cryptography. Almost all of our current digital security infrastructure is based on the concept of multiplying large numbers together modulo suitably big prime numbers.

Any major step towards understanding them (such as a closed-form equation for primes) would have major mathematical knock-on effects which may or may not undermine these methods, or provide us with a basis for even stronger cryptographic mechanisms to make use of in the future.

Re: Is This Prime?

#16

Is there a reason we're obsessed with primes beyond aesthetics? Why does this set of numbers garner all the headlines as opposed to some other arbitrary integer sequence like the Recamán numbers [0] ? If tomorrow someone discovered a closed-form equation for the nth prime, how would mathematics/the world change? [0] https://en.wikipedia.org/wiki/Recamán%27s_sequence

Your original link 404'd on me (you seem to have replaced it with a different one though). Here's the working Wikipedia link: https://en.wikipedia.org/wiki/Recamán%27s_sequence

Thanks. I've edited the link.

Re: Is This Prime?

#17
This reminds me of my favorite in-person magic trick to do.

First, memorize all the two-digit primes. 25 numbers isn't that hard to memorize.

Then, tell someone "Oh, I can instantly tell whether a number is prime or not. Give me a number, I'll tell you whether it's prime."

If they tell you a number between 1 and 100, use your memorized list. Otherwise, it's a game of cold reading; if they just generated a random string of many digits, there's a low chance that the number actually is prime. "21923847" is a keysmash, and it's almost certainly not prime, because the frequency of primes goes down as numbers get bigger. And most people will ask you a number, hear "no", and then go check the number's primality. Eventually, they'll look up a number in advance; that number is almost certainly prime.

Re: Is This Prime?

#20

When I was a fifth grader in China, we were required to memorize all prime numbers below 100. Curious if that is common in other countries?

I don't think so. Remember any other interesting numbers list you needed to memorize?
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