[ktallett]

As someone who struggles slightly with maths despite working in physics and engineering, I am always in awe of those who can do math so easily. You do occasionally come across those who can do math with minimal intermediate steps and it is mind blowing to watch.

[Suppafly]

I think he was doing the intermediate steps, but just posting the answer to draw out other people to do the intermediate steps, to see how other people were approaching it.

[v9v]

The way I had understood it was that the author arrived at these problems by incrementally modifying complicated integral formulas just up to the point where Mathematica couldn't solve them, and then used the solution from Mathematica for the previous iteration, his intuition and some ad-hoc methods to make an educated guess for the answer for the "unsolvable" integral. I suppose those can be called intermediate steps, but not in the usual sense.