Taking the absolute value of everything, the series is 1, 5, 9, 13, 17, 21, etc.. If you take the differences between successive elements, you get 4, 4, 4, 4, etc., which tells you that the series can be expressed as 4*0 + 1, 4*1 + 1, 4*2 + 1, etc. An easy way to express this would be an = 4n + 1, having the first element, 1, as a0. If you wanted 1 to be a1 instead, then you would have an = 4(n-1) + 1 = 4n + 1 - 4 = 4n - 3. Afterwards, just add in the (-1)n or (-1)n+1, depending on which way you chose to describe the series.
King Author wrote:If space (rather, distance) is an illusion, it'd be possible for one meta-me to experience both body's sensory inputs.
Yes. And if wishes were horses, wishing wells would fill up very quickly with drowned horses.