log(2) = 0.301029996
Binary Search Tree Worst case is [Log2(N)+1]

N=10      log(10) =    1  / .301029996  = 3  + 1 =  4  , a tree with a height of 4  could have  (2^4)-1  = 15       nodes  
N=100     log(100)=    2  / .301029996  = 6  + 1 =  7  , a tree with a height of 7  could have  (2^7)-1  = 127      nodes
N=1000    log(1000)=   3  / .301029996  = 9  + 1 =  10 , a tree with a height of 10 could have  (2^10)-1 = 1023     nodes
N=10000   log(10000)=  4  / .301029996  = 13 + 1 =  14 , a tree with a height of 14 could have  (2^14)-1 = 16383    nodes
N=100000  log(100000)= 5  / .301029996  = 16 + 1 =  17 , a tree with a height of 17 could have  (2^17)-1 = 131071   nodes
N=1000000 log(1000000)=6  / .301029996  = 19 + 1 =  20 , a tree with a height of 20 could have  (2^20)-1 = 1048575  nodes