When I watched Andrej Karpathy's NN videos a year or two back, I trained a Neural Network to multiply an integer by two. This was with a rather small training

When I watched Andrej Karpathy's NN videos a year or two back, I trained a Neural Network to multiply an integer by two. This was with a rather small training set but if you rounded the results (which was a floating point), they were mostly correct. For positive numbers. My training data didn't include any negative numbers so they were hilariously bad.