Liar Numbers - Numberphile
Fermat's "Little" Theorem is great - but beware of Fermat Liars and tricky Carmichael Numbers. More links & stuff in full description below ↓↓↓ Continues at: http://youtu.be/HvMSRWTE2mI...
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>> DR GRIME: Let's have a look at one of these tests that they have, that they apply to seeif a number is prime or not. Well we're going to use a fact I have mentioned before when talkingabout primes and we're going to use Fermat's Little Theorem. It's a theorem about primenumbers and what it says is that if you have a number which I'll call 'a' and I'm goingto raise it to a power 'prime number' so that's called 'p prime', and I subtract the originalnumber then I say that this is divisible by p. There you go.So if a number is prime that's always true for whatever number 'a' you pick. So, let'sdo an example of thi...
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>> DR GRIME: Let's have a look at one of these tests that they have, that they apply to seeif a number is prime or not. Well we're going to use a fact I have mentioned before when talkingabout primes and we're going to use Fermat's Little Theorem. It's a theorem about primenumbers and what it says is that if you have a number which I'll call 'a' and I'm goingto raise it to a power 'prime number' so that's called 'p prime', and I subtract the originalnumber then I say that this is divisible by p. There you go.So if a number is prime that's always true for whatever number 'a' you pick. So, let'sdo an example of thi...
