Largest prime < largest prime < n.

Terms

a(0) =2a(1) =2a(2) =3a(3) =3a(4) =5a(5) =5a(6) =5a(7) =5a(8) =7a(9) =7a(10) =11a(11) =11a(12) =11a(13) =11a(14) =13a(15) =13a(16) =17a(17) =17a(18) =17a(19) =17a(20) =19a(21) =19a(22) =19a(23) =19a(24) =19a(25) =19a(26) =23a(27) =23a(28) =29a(29) =29