algorithm is based on the number of posts required at each level: (so far 25, 50, 100, 200, 300)
Actually isn't it 25,25,50,100,200,300 so far, like the 1,1, at the start of the Fibonacci sequence?
Contrary to popular belief (at the base of many intelligence tests etc), there is no uniquely defined, "correct" way of continuing any finite number sequence.