a(1) = 4. a(n) = A222209(a(n-1)).

Terms

a(0) =4a(1) =5a(2) =7a(3) =11a(4) =19a(5) =37a(6) =71a(7) =151a(8) =379a(9) =1051a(10) =3307a(11) =11483a(12) =44453