A good answer might be:
The base case of the definition.
Base Case of the Pyramid
A recursive definition (or a recursive algorithm) needs two parts:
- If the problem is easy, solve it immediately.
- If the problem can't be solved immediately,
divide it into smaller problems, then:
- Solve the smaller problems by applying this procedure to each of them.
In terms of pyramidal numbers, this is:
Pyramid(1) = 1
Pyramid(N) = Pyramid(N-1) + Triangle(N)
Oddly, the base case for pyramidal numbers is the peak of the pyramid.
Oh, oh... this definition uses
Triangle(N) without saying anything
about it. Is this wrong?