The Collatz conjecture is a conjecture in mathematics that concerns a sequence defined as follows: start with any positive integer n. Then each term is obtained from the previous term as follows: if the previous term is even, the next term is one half the previous term.
The Dutch (Dutch), occasionally referred to as Netherlanders—a term that is cognate to the Dutch word for Dutch people, "Nederlanders"—are a Germanic ethnic group native to the Netherlands.
A mathematician is someone who uses an extensive knowledge of mathematics in his or her work, typically to solve mathematical problems.
The On-Line Encyclopedia of Integer Sequences (OEIS), also cited simply as Sloane's, is an online database of integer sequences.
A philosopher is someone who practices philosophy, which involves rational inquiry into areas that are outside either theology or science.
In algebra, the 3x + 1 semigroup is a special subsemigroup of the multiplicative semigroup of all positive rational numbers.