Arithmetic Progression Series Sum

Let a1,a2,a3,... be in an arithmetic progression of positive terms.
Let Ak=a1‌2−a2‌2+a3‌2−a4‌2+...+a2k−1‌2−a2k‌2.
If A3=−153,A5=−435 and a1‌2+a2‌2+a3‌2=66, then a17−A7 is equal to ______.