a(1)=2, a(n+1) = 2*a(n) - phi(a(n)) where phi is the Euler totient function A000010.

Terms

a(0) =2a(1) =3a(2) =4a(3) =6a(4) =10a(5) =16a(6) =24a(7) =40a(8) =64a(9) =96a(10) =160a(11) =256a(12) =384a(13) =640a(14) =1024a(15) =1536a(16) =2560a(17) =4096a(18) =6144a(19) =10240a(20) =16384a(21) =24576a(22) =40960a(23) =65536a(24) =98304a(25) =163840a(26) =262144a(27) =393216a(28) =655360a(29) =1048576