a(1) = 2, a(n+1) = smallest squarefree number == 1 (mod a(n)) and > a(n).

Terms

a(0) =2a(1) =3a(2) =7a(3) =15a(4) =31a(5) =94a(6) =95a(7) =191a(8) =383a(9) =767a(10) =1535a(11) =3071a(12) =6143a(13) =12287a(14) =36862a(15) =36863a(16) =73727a(17) =147455a(18) =294911a(19) =589823a(20) =1179647a(21) =2359295a(22) =4718591a(23) =9437183a(24) =18874367a(25) =37748735a(26) =75497471a(27) =150994943a(28) =301989887a(29) =905969662