Earliest sequence with a(a(n)) = n^4.

Terms

a(0) =0a(1) =1a(2) =3a(3) =16a(4) =5a(5) =256a(6) =7a(7) =1296a(8) =9a(9) =4096a(10) =11a(11) =10000a(12) =13a(13) =20736a(14) =15a(15) =38416a(16) =81a(17) =18a(18) =83521a(19) =20a(20) =130321a(21) =22a(22) =194481a(23) =24a(24) =279841a(25) =26a(26) =390625a(27) =28a(28) =531441a(29) =30