a(n) = ceiling((sqrt n)^(sqrt n)).

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =7a(5) =9a(6) =14a(7) =19a(8) =27a(9) =39a(10) =54a(11) =74a(12) =102a(13) =140a(14) =190a(15) =256a(16) =345a(17) =461a(18) =613a(19) =812a(20) =1071a(21) =1407a(22) =1843a(23) =2404a(24) =3125a(25) =4051a(26) =5234a(27) =6743a(28) =8663a(29) =11099