Generic to find the square of a number. Based on this TS challenge: https://github.com/type-challenges/type-challenges/blob/main/questions/27133-medium-square/README.md

FindSquare.ts

// Generates array from 0 to N (inclusive)
type GenerateArr<N extends number, Acc extends number[] = []> = Acc['length'] extends N
  ? Acc
  : GenerateArr<N, [...Acc, Acc['length']]>

type FlattenArr<A extends unknown[]> = A extends [infer X extends number[], ...infer R] ? [...X, ...FlattenArr<R>] : A;

type AbsoluteSquare<N extends number, Acc extends unknown[] = []> = 
  Acc['length'] extends N 
    ? FlattenArr<Acc>['length']
    : AbsoluteSquare<N, [...Acc, GenerateArr<N>]>

type Square<N extends number> = `${N}` extends `-${infer NonNegNum extends number}` 
  ? AbsoluteSquare<NonNegNum> 
  : AbsoluteSquare<N>