I understand that you want to create a neural network with multiple hidden layers instantiated using a for loop. The fitnet function can be provided a vector of hidden layer sizes. Assuming the same size for each hidden layer:
trainFcn = 'trainlm';
n = 5; % Number of hidden layers
s = 10; % Size of each hidden layer
layerSizes = ones(1, n)*s % Creating vector with layer sizes
net = fitnet(layerSizes, trainFcn);
Alternatively, if the layers have varying sizes, for instance in reducing powers of two:
trainFcn = 'trainlm';
n = 5; % Number of hidden layers
layerSizes = zeros(1,n);
for i = 1:n
layerSizes(i) = 2^(n-i+1);
end
net = fitnet(layerSizes, trainFcn);
