Largest prime power <= n.

Terms

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