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Hello,
Hello! For this problem, I randomly guessed the sequence:
a1=-4
a2=-2
a3=1
a4=1
a5=1
a6=1
a7=1
a8=1
So a1+a2+...+a8=0, and a1*a2*...*a8=8, so it satisfies and n congruent to 0 (mod 4).
Is there are more rigorous way to do this?
Thanks,
Tina Jin
First consider: is $n$ even or odd?
I understand now! When n=odd, the sum of ai cannot be even number (namely cannot be 0). When n=even, there must be more than 1 even ai, so n is a multiple of 4 and therefor congruent to 0 mod 4.
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