Map incrementing integer range to six-digit base 26 max, but unpredictably

Question

I want to design a URL shortener for a particular use case and type of end-user that I have targetted. I have decided that I want the URLs to be stored internally according

Answer 1

How about an LFSR? The linear feedback shift register is used to generate pseudo-random numbers in a range - the operation is deterministic given the seed value, but it can visit every value in a range with a long cycle.