>Good thing all source code is just very convenient mathematical notation describing an algorithm

Only really true for pure functions (i.e. same input -> same output + side effects), I think. A lot of the code in actual practice is stuff like "update this bit of object state", "set this server variable so that it does this"; and it really doesn't generalize beyond a very specific platform.

Those may still technically count as algorithms, but not in the sense people normally think of them.

Although the ones they try to patent generally are of the "pure function" type, so it may be a distinction without a difference.