For n <= 1 there are no 2-small-step numbers in the interval 2^n until 2^(n+1).
For 2 <= n <= 6 there are
(1,4,9,17,27)_n
many 2-small-step numbers in the interval 2^n until 2^(n+1).
For any n >= 7 there are
n^2-n-2
many 2-small-step numbers in the interval 2^n until 2^(n+1).
For 2 <= n <= 5 there are (1,5,14,31)_n many 2-small-step numbers < 2^(n+1).
and for any n >= 6 there are (n^3-7n)/3 many 2-small-step numbers < 2^(n+1).