I can't give the correct number of parameters of AlexNet or VGG Net.

For example, to calculate the number of parameters of a conv3-256 layer of VGG Net, the answer is 0.59M = (3*3)*(256*256), that is (kernel size) * (product of both number of channels in the joint layers), however in that way, I can't get the 138M parameters.

So could you please show me where is wrong with my calculation, or show me the right calculation procedure?