A multilayer perceptron that can approximate any continuous function on compact subsets of real numbers, as first demonstrated by Cybenko (1989) and Hornik (1991).

Implemented in Mathematica 11

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Cybenko, G. (1989). Approximation by superpositions of a sigmoidal function. MCSS, 5, 455.
Hornik, K. (1991). Approximation capabilities of multilayer feedforward networks. Neural Networks, 4, 251-257.