I'm looking for a puzzle book to get my Dad for his birthday, and he's very much a mathematician and loves puzzles. I'm trying to find essentially a compendium of challenging integrals (or maths in general). I'd be looking for questions around a Masters student's level, so quite challenging questions.
I've come across 'Irresistible Integrals' and 'A treatise on the integral calculus; with applications, examples and problems' but neither are quite what I'm looking for, they're both very textbook-y.
I'm trying to find something which isn't trying to teach calculus, but just straight up challenges with solutions. Questions similar to ones in, for example, the MIT Integration Bees. I tried looking for a collection of MIT Integration Bee questions, but couldn't find one.
Thanks for reading, has anyone got any ideas? It'd be greatly appreciated.
For anyone reading this, I ended up getting 'The William Lowell PUTNAM Mathematical Competition Problems and Solutions'. There are 3 editions, and are very much what I was looking for :)
See: The William Lowell Putnam Mathematical Competition 1985–2000