Yes, I do read carefully.

He only mention n = 2, 3, 4 .. is infinite. not a or b.

ofcouse n = 2, 3, 4,... is infinite.  but a or b should be proved.

like (1/2)^(1/2) = (1/4)^(1/4)  we can make it like (1/n)^(1/n)  n = 2 or 4 should be same.  不同的变量 2， 3， 4。。 它们的结果有可能一样。

上面你说的递增递减。是要证明的。要有数学表达。这才可称完整。