According to stem analysis, it can be concluded that building 1 floor needs 1 2δ, building 2 needs two 2δ, building 3 needs three 2δ,

Accordingly, it can be concluded that n layers need n 2 increments,

When n= 10,10 2 =100 (pieces),

When n 2 =49 and n=7,

So the answer is:100; 7; n 2。