a(1)=2. a(n) is the a(n-1)st integer from among those positive integers coprime to a(n-1).

Terms

a(0) =2a(1) =3a(2) =4a(3) =7a(4) =8a(5) =15a(6) =28a(7) =65a(8) =87a(9) =134a(10) =271a(11) =272a(12) =577a(13) =578a(14) =1227a(15) =1844a(16) =3695a(17) =4624a(18) =9825a(19) =18562a(20) =37127a(21) =37537a(22) =37538a(23) =75627a(24) =113480a(25) =283799a(26) =283800a(27) =1198543a(28) =1201967a(29) =1302144