Concept
Fermats little theorem — where it appears
2 essays name this object, across 2 fields. What follows is each of them, and the objects they name alongside it.
Also named here as order — the same set of essays touches all of them, so they are one junction rather than several.
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.
Necklaces that prove a theorem
Thread five beads in two colours, thirty-two ways. Two of them are all one colour; the other thirty fall into rings of five. That count, and nothing else, is Fermat's little theorem.
Named alongside it
The objects these essays reach for when they reach for this one.
Cyclic groupModular arithmeticOrderPrimesCounting two waysGreatest common divisorGroup actionOrbitParityPeriodicityPrimality testRemainder