Once you guess the formula, the proof is just a few lines of calculus. It's accessible to anyone who has taken Calc I, I think. The full text .pdf of the origin

Once you guess the formula, the proof is just a few lines of calculus. It's accessible to anyone who has taken Calc I, I think. The full text .pdf of the original paper [0] is freely available; the result is Theorem 1, whose proof is on pages 2 and 3. I believe the formula was found by computer search, but my memory could be failing me. The three people the result is named after are all well-known for computer-assisted mathematics, for instance using the PSLQ algorithm [1]. [0]: https://www.ams.org/journals/mcom/1997-66-218/S0025-5718-97-00856-9/home.html https://www.ams.org/journals/mcom/1997-66-218/S0025-5718-97-... [1]: https://en.wikipedia.org/wiki/Integer_relation_algorithm https://en.wikipedia.org/wiki/Integer_relation_algorithm