Is (-1)^(2n) * (1 / n) an alternating series

my textbook says that an alternating series is a series whose terms are alternatively positive and negative, but this video (link below), says that it's a alternating series.

http://www.youtube.com/watch?v=-K9Qt6YUI…

So is it or isn't it?

assuming n is positive integer

then 2n is always even

2*1 = even 2
2*2 = even 4
2*3 = even 6

any number to the even exponent is positive

(-1)^2 = 1
(-1)^4 = 1
(-1)^6 = (-1)*(-1)*(-1)*(-1)*(-1)*(-1)

so its positive

if all the elements of a series are positive then NO IT is NOT a alternating series