Tweets about algebra, number theory, and miscellaneous math by @JohnDCook.
Joined January 2010
- Tweets 15,249
- Following 19
- Followers 194,735
- Likes 208
1,991 Photos and videos
Jun 12
Not in geometric mean.
x.com/thekriskay/status/2065…
if you have a $1 net worth,
you are closer to the 2nd richest person on earth, than he is to Elon.
read that again.
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Jun 11
An algebraic number field is a finite degree extension of the rationals
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Jun 10
Conway's Little Theorem: A triangle is equilateral if and only if the ratio between the length of any two sides is rational and the ratio between any two angles is also rational.
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Jun 10
Every prime number of the form 4n 1 is the sum of two squares in exactly one way.
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Jun 10
Pulling on a thread:
How an approximation lead to a series of nine posts.
johndcook.com/blog/2026/06/1…
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Jun 9
Mentally calculate scientific calculator functions to around two significant figures. johndcook.com/blog/mental-fu…
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Jun 8
Let f(n) be the nth Fibonacci number. Then f(mn) is divisible by f(m)f(n) iff gcd(m,n) = 1, 2, or 5.
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Jun 8
If m divides n, then b^m - 1 divides b^n - 1 for all b > 1.
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Jun 5
For positive integer n, f(n) = 2^(2^(n 1)) 2^(2^n) 1 has at least n 1 distinct prime factors. cut-the-knot.org/proofs/Infi…
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Jun 5
Mentally testing for divisibility by a sequence of primes johndcook.com/blog/2023/03/0…
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Jun 4
The pair (p, p 2) are twin primes iff 4((p-1)! 1) p = 0 mod p(p 2). -- Clement's theorem
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