for r=1:5
   vol = (4/3)*pi*r^3;
   disp([r, vol])
end;

for r=1:5
   for s=1:r
      vol = (4/3)*pi*(r^3-s^3);
      disp([r, s, vol])
   end
end;

for i=1:6
   for j=1:20
      if j>2*i, break, end
      disp([i, j])
   end
end;

