How to check output after FPGA Implementation?
There are several possibilities:


You can use ChipScope. That's an on-chip logic anaslyzer, which is synthesized into your design.
You can implement (or use) a FPGA to PC communication like UART to write numbers and read results.
You can implement a testcase in hardware (like your testbench) that enlights a LED if the testcase is passed.
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