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Depending what you are using the numbers for, this might be fine. If you just need a random interval, get a number from the table method he describes in the article and apply it to a timer for a delay (either in seconds, minutes, with post-scaling or without).
If your compiler supports the rand function, then go ahead and use it to generate the delay between LED OFF and LED ON. Beware that the program using the rand function will give the same string of "random" numbers every time the micro is reset. It will appear to be random, but nothing generated by an algorithmic function really is.
One way to seed using the srand function is to take a number from a free running timer based on when the user last pushed a button, etc.