f()=2
f(0)=4
f(0,0)=f(4)=16
f(0,0,0)=f(16,16)
f(0,0,0,0)=f(f(16,16),f(16,16),f(16,16))
f(0,0,0,0,0)=f(f(f(16,16),f(16,16),f(16,16)),f(f(16,16),f(16,16),f(16,16)),f(f(16,16),f(16,16),f(16,16)),f(f(16,16),f(16,16),f(16,16)))

f(n)=2^(n+2)

f(1,0)=2^18
f(2,0)=2^(2^18)
f(3,0)=2^(2^(2^18))
f(4,0)=2^(2^(2^(2^18)))

f(0,1)=f(f(0,0),0)=f(16,0)=2^(2^(2^(2^(2^(2^(2^(2^(2^(2^(2^(2^(2^(2^(2^(2^18)))))))))))))))
f(1,1)=f(f(0,1),0)=f(f(16,0),0)
f(2,1)=f(f(1,1),0)=f(f(f(16,0),0),0)
f(3,1)=f(f(2,1),0)=f(f(f(f(16,0),0),0),0)

f(0,2)=f(f(0,1),1)=f(f(16,0),1)
f(1,2)=f(f(0,2),1)=f(f(f(16,0),1),1)
f(2,2)=f(f(1,2),1)=f(f(f(f(16,0),1),1),1)
f(3,2)=f(f(2,2),1)=f(f(f(f(f(16,0),1),1),1),1)

f(0,3)=f(f(0,2),2)=f(f(f(16,0),1),2)
f(1,3)=f(f(0,3),2)=f(f(f(f(16,0),1),2),2)
f(2,3)=f(f(1,3),2)=f(f(f(f(f(16,0),1),2),2),2)
f(3,3)=f(f(2,3),2)=f(f(f(f(f(f(16,0),1),2),2),2),2)