In this video we use an array node to provide 3 float2's for sampling the texture. You can of course also calculate some kind of UV offset based on the 'operator i'.
To use the 'operator i' inside your for-loop 'calculation', you select the 'String' node you used for the 'Operator'.
Set the 'Value Type' to 'Shader / Integer'.
This will change the 'As Value' output of the 'String' node to an integer you can now use in the rest of your node network inside the loop.