You can use UpdateAttribute Processor by storing the state and incrementing the last state value then pass the attribute value to get HTTP response.
As GetHTTP processor doesn't accept any incoming connections use InvokeHTTP processor instead of GetHTTP processor.
In this processor i'm using getStateValue function to get the value for the variable and adding one to it so output flowfile from UpdateAttribute will have seq attribute with 1 as value in your first run.
Then use the attribute in your InvokeHTTP processor to increment the page number.
Refer to this link if you want to reset the state once the number reaches to limit.
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