"...calculate row n of Pascal’s triangle or implement a basic sorting algorithm, for example"...

I assume you let your candidate use google to search for solutions to these problems if they ask ?

Personally speaking, I think if you are going to put an engineer on the spot about some stuff they may or may not be familiar with, you have to allow them the appropriate toolset to solve these problems...you see for me, asking a dev to implement a sort algorithm or solution pascal's triangle doesn't really tell me a whole lot on its own, especially if the person has no entries in his "memory" for these problems, I think it is unfair and probably irrelevant to what they may do in a normal situation.