* Hexagonal number sequence
A hexagonal number sequence is a sequence of figurate numbers where the nth hexagonal number hₙ is the number of distinct dots in a pattern of dots consisting of the outlines of regular hexagons with sides up to n dots, when the hexagons are overlaid so that they share one vertex.
This program returns the hexagonal number sequence of n length.
* Update hexagonalnumbers.py
* Update hexagonalnumbers.py
* Update hexagonalnumbers.py
* Update hexagonalnumbers.py
* Update and rename hexagonalnumbers.py to hexagonal_numbers.py
* Length must be a positive integer
Co-authored-by: Christian Clauss <cclauss@me.com>
