Also V.I. Arnol'dV.I. Arnol'd is quite enthusiastic about the experimental mathematics. In particular, he wrote two books on the subject in Russian, Experimental mathematics, Fazis, Moscow, 2005, and Experimental observation of mathematical factsExperimental observation of mathematical facts, MCCME, Moscow, 2006, where, I guess, one could find a number of examples of the kind you ask for. Unfortunately, to the best of my knowledge, neither of these books was translated into English so far.