As The Book of F# is nearing completion I’ve suddenly found myself with a bit of something people like to call spare time. This concept has been pretty foreign to me over the past nine months so as a way to fill that time I started looking at the Project Euler problems. I’m not far along yet (my math skills have gotten rusty over the years) but so far it has been a fun exercise.

Problem 2, involves calculating the sum of the even Fibonacci numbers less than 4,000,000. In the spirit of the project, I won’t divulge my entire solution (though it won’t be hard to fill in the gaps), but I thought the algorithm for generating Fibonacci numbers was interesting so I wanted to explore it a bit along with some interesting ways we can use it to create sequences in F#. (more…)