Hello from MrBillDoesMath!
Answer:
a(n) = (-1)^(n+1) * ( 2 ^ (2n+1) ) where n = 0, 1, 2, etc.
Discussion:
-2 = (-1) * 2^1
8 = (+1) 2^3
-32 = (-1) * 2^5
128 = (+1)* 2^7
In general,
a(n) = (-1)^(n+1) * (2 ^ (2n+1)) where n = 0, 1, 2, etc.
Regards,
MrB
P.S. I'll be on vacation from Friday, Dec 22 to Jan 2, 2019. Have a Great New Year!
