Question 1024880
<pre>
(-1)^(int((n-1)/4)+int((n+1)/4))

where int(x) = the greatest integer not exceeding x.
This function is often denoted floor(x).

So it could be written

(-1)^(floor((n-1)/4)+floor((n+1)/4))

Texas Instrument calculators use int(x).

Edwin</pre>