a(1) = 2, a(n+1) is the largest squarefree number < 2*a(n).

Terms

a(0) =2a(1) =3a(2) =5a(3) =7a(4) =13a(5) =23a(6) =43a(7) =85a(8) =167a(9) =331a(10) =661a(11) =1321a(12) =2641a(13) =5281a(14) =10561a(15) =21121a(16) =42241a(17) =84481a(18) =168961a(19) =337921a(20) =675841a(21) =1351681a(22) =2703361a(23) =5406721a(24) =10813441a(25) =21626881a(26) =43253761a(27) =86507521a(28) =173015041a(29) =346030081