The number of pieces used in the first I-shaped pattern is 5×1+2 = 7;

The number of pieces used in the second I-shaped pattern is 5× 2+2 =12;

The number of pieces used in the third I-shaped pattern is 5× 3+2 =17;

…

It can be found that which I-shaped pattern needs the number of pieces equal to the product of 5 and a few plus 4.

Therefore, the number of blocks of the fifth I-shaped pattern * * * is 5× 5+2 = 27;

The number of blocks for the nth I-shaped pattern is 5× n+2 = 5n+2.

So, the answer is: 27; 5n+2。