Problem on article Segment Tree

[Blume-Piyush]

Article: Segment Tree

Problem:
The article states that Maximum number of nodes a segment tree would have is 4N, but if you look at the equation, maximum number of nodes a segment tree would have is 2N - 1.

[Bhaskar1312]

Say your array has a size of N = 2^k+1 for which you want to find the sum of elements [l, r] where 0<=l,r<=N-1
Now in the segment tree, the number fo leaf nodes has to be 2^(k+1) (rounded up by two factor) and
since the leaf nodes are 2^(k+1), the total number of nodes would be 2^(k+2) ~ 4N