This answers reminds me of the following — probably apocryphal — story. When the MRDP theorem was proved, some great Soviet mathematician (maybe Kolmogorov?) was told about it in the form “there is a multivariate polynomial with integer coefficients whose positive values are exactly the prime numbers”, and he exclaimed: “this is wonderful! we will learn many new fascinating things about prime numbers thanks to this!”. But then he was told that it applies to any computably enumerable set and he lamented: “this is disastrous! then we won't learn anything new at all!”.
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