Elements ={1,2,3,4,5,6,7}
Root node is 4. // Root is at level '0' assume.
if 2 and 6 are present at level 1 then order of ${\color{Red} 1,{\color{Red} 3,{\color{Red} 5,{\color{Red} 7}}}}$ is not necessary
because it is balanced.This can be done in 4! ways.
And level 1 nodes ${\color{Red} 2,{\color{Red} 6}}$ also change in 2! ways.
Hence total no of orders=4!*2!=48.
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Like one order is 4,${\color{Red} 2,{\color{Red} 6}}$,${\color{Green} 1,{\color{Green} 3,{\color{Green} 5,{\color{Green} 7}}}}$
Red color can be permuted and green color can be permuted no problem for AVL tree balanced factor.
I)4,2,6,1,3,5,7
II)4,2,6,3,1,5,7
....
These orders are not cause any problem for AVL property.