Concept
Greatest common divisor
2 essays name this object, across 2 fields. What follows is each of them, and the objects they name alongside it.
The oldest algorithm, drawn as a tiling
Euclid's method for finding a greatest common divisor is usually presented as a loop. It is also a way of tiling a rectangle with squares, and the tiling explains why it works.
Numbers that wrap
A clock does arithmetic. It has finitely many numbers, addition never leaves it, and multiplication behaves entirely differently depending on one property of the size of the dial.
Named alongside it
The objects these essays reach for when they reach for this one.
Continued fractionsCyclic groupFermats little theoremFibonacciIncommensurabilityLamé's theoremModular arithmeticOrderParityPeriodicityPrimesRemainder