lb = -500;
hb = 500;
total = hb - lb;
x = linspace(lb,hb,total);
for n = (lb:hb)-lb+1,
  if n >= 2
    x(n) = (1/4)^n;
  else
    x(n) = 0;
  end
end
h = linspace(lb,hb,total);
for n = (lb:hb)-lb+1,
  if n < 2
    h(n) = 2^n;
  else
    h(n) = 0;
  end
end


ny = [2*lb:2*hb];
y = conv(x,h);
