Totient
Named by 2 essays across one field — each of them below, with the objects they name alongside it.
Which polygons can be drawn
Three sides yes, seven no, seventeen yes. The list of constructible regular polygons is neither everything nor almost nothing, and the pattern in it is a fact about which numbers are one less than a power of two.
Every element is a power of one of them
Pick the right element of a finite field and its powers run through every other non-zero element exactly once before returning to one. Multiplication becomes addition of exponents, and a table of q − 1 entries replaces the whole multiplication table.
Named alongside it
The objects these essays reach for when they reach for this one.
Cyclic groupConstructible numberCounting argumentDegree of an extensionDiscrete logarithmFermat primeFermats little theoremFinite fieldModular arithmeticPrimitive elementRational root theoremRegular polygon