How to implement Python's MLPClassifier with gridsearchCV?
A tuple of the form $(i_1, i_2, i_3, ... , i_n)$ gives you a network with $n$ hidden layers, where $i_k$ gives you the number of neurons in the $k$th hidden layer. 

If you want three hidden layers with $10,30$ and $20$ neurons, your tuple would need to look like $(10,30,20)$.

$(100,1)$ would mean that the second hidden layer only has one neuron.