4   7   12   19   28   A   52
A ² ? 4 = ?

The given series is in the below pattern,
First term = 4
Second term = First term + 3
? Second term = 4 + 3 = 7
Third term = Second term + 5
? Third term = 7 + 5 = 12
Fourth term = Third term + 7
? Fourth term = 12 + 7 = 19
Fifth term = Fourth term + 9
? Fifth term = 19 + 9 = 28
Sixth term = Fifth term + 11
? Sixth term = 28 + 11 = A
? A = 39
So, 39 will come in place of A.
Similarly , we can find all others terms also.
now , A² ? 4 = 39² ? 4 = 1517
Hence ? = 1517