Floor[(n^n)^(1/3)].

Terms

a(0) =1a(1) =1a(2) =3a(3) =6a(4) =14a(5) =36a(6) =93a(7) =256a(8) =729a(9) =2154a(10) =6583a(11) =20736a(12) =67156a(13) =223150a(14) =759375a(15) =2642245a(16) =9387368a(17) =34012224a(18) =125537306a(19) =471556031a(20) =1801088541a(21) =6989288906a(22) =27536796142a(23) =110075314176a(24) =446169698823