4-full numbers: if a prime p divides k then so does p^4.

Terms

a(0) =1a(1) =16a(2) =32a(3) =64a(4) =81a(5) =128a(6) =243a(7) =256a(8) =512a(9) =625a(10) =729a(11) =1024a(12) =1296a(13) =2048a(14) =2187a(15) =2401a(16) =2592a(17) =3125a(18) =3888a(19) =4096a(20) =5184a(21) =6561a(22) =7776a(23) =8192a(24) =10000a(25) =10368a(26) =11664a(27) =14641a(28) =15552a(29) =15625