Least m such that phi(x)=2m has exactly n solutions.

Terms

a(0) =5a(1) =1a(2) =2a(3) =4a(4) =6a(5) =16a(6) =18a(7) =20a(8) =12a(9) =24a(10) =80a(11) =198a(12) =1134a(13) =352a(14) =156a(15) =36a(16) =168a(17) =108a(18) =468a(19) =72a(20) =312a(21) =528a(22) =880a(23) =180a(24) =1280a(25) =192a(26) =144a(27) =660a(28) =1848a(29) =120