Last night, on our way to the fireworks in Antwerp, we walked by this definition of prime numbers:

“The numbers, only divisible by $1$ and itself are: $2,3$ and every number before or after a multiple of $6$, without their squares or products.” (Peter Wynen)

True enough.

And a lot more user-friendly than: the generators of the multiplicative monoid of all natural numbers which are $\pm 1$ modulo $6$ are the prime numbers, except for $2$ and $3$.

I wish you a 2018 full of math (and artistic) pleasures.

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