Plot of the running time of the Euclidean algorithm for gcd(x,y). Red indicates a fast computation, while successively bluer points indicate slower computations.
Rational approximations to regular octagons, with coordinates derived from the Pell numbers.
Time-keeping on a clock gives an example of modular arithmetic, the "clock group" is represented by the group Z/12Z for a 12-hour clock and Z/24Z for a 24-hour clock.
Graph of the number of ways to write an even number n as the sum of two primes (4 ≤ n ≤ 1,000,000). This is the main object of study of the Goldbach's conjecture
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