Like Star Strider mentioned, you can use all() or any()
a(i)>0 && ~any(a(i-32:i-1))
but there are a couple things to mention.
First is whether a is an integer class. If it's not, then testing for equality with zero is likely going to cause problems. Test to within some tolerance.
a(i)>0 && all(abs(a(i-32:i-1)-0)<tolerance)
Second is whether you're making sure a(i-32), etc exist. You may need to pad the vector or restrict the indexing accordingly.