Someone asked me to identify this short story whose title or author’s name they can’t remember at all. This supposedly was published in the 1960’s or 1970’s in Analog magazine. In this story someone infiltrates a think tank or some similar sort of research institution in order to figure out what they have been doing research on. He discovers that they have been trying to prove that 2 plus 2 equals 4.
As is usual in these “Identify the Story” threads, I suspect that the person has got the plot of the story thoroughly mixed up. Anything close to this plot is worth mentioning. The person insists that this is not a confused memory of Isaac Asimov’s _The Feeling of Power."
I think your story is “Trurl’s Machine,” by Stanislaw Lem.
I doubt it. No thiink tank (well, maybe literally), and it was 2 plus 2 equals 7 
Could you give me a reasonable summary of “Trurl’s Machine” so I can judge whether it resembles in any way the plot summary that I was told about?
Trurl’s Machine is a story from a series of fables about two robotic constructors - Trurl and Clapaucius. Trurl builds great (eight stories tall) thinking machine and when finished ask in an off-hand way, just for test, how much is two plus two. Machine answer is seven. He groans, starts doing some extra clanking and asks again. Machine still claims it’s seven. Meanwhile Clapaucius come to visit Trurl, but despitetheir efforts they still fails to find bug. Eventually desperate Trurl starts to kick machine. It takes offense and raises from it’s base and starts chasing both constructors with intention to crush them - or make them admit that two plus two is seven. Eventually they escape into mountains and hide in a cave. Machine enraged by Trurl repeating that two plus two is four starts banging into cave entrance and eventually broke itself and falls down. Last words of broken machine in response to Trurl “Two plus two is…” are “…seven”.
Man, I love Fairytales for Robots.