I'm gonna' be honest, Anonymous....I "borrowed" this "formula" from one of our fellow posters, Nauseated, based on his answer to a problem just last week....I haven't had time to digest the rationale behind it, yet.
However.......here is his "non-technical" explanation.....if you care to look at it....
{It's the fourth answer from the bottom}.........http://web2.0calc.com/questions/each-small-square-has-a-side-length-of-one-unit-how-many-distinct-paths-of-six-units-are-there-from-a-to-b
Thanks for that, ThisGuy .......
I''ve heard about the Madlebrot Set - a form of tiling - before.
The hexa-flexagon thing was a new one......!!!
P.S. - If you like such things, you may want to get your hands on a copy of the book, Asimov on Numbers, written by - well, you guessed it - Isaac Asimov. It's not hard to read, and it contains short articles on various math topics.....all of them presented in the "quirky" style of Asimov.