Powers of cube root of 21 rounded up.

Terms

a(0) =1a(1) =3a(2) =8a(3) =21a(4) =58a(5) =160a(6) =441a(7) =1217a(8) =3357a(9) =9261a(10) =25551a(11) =70492a(12) =194481a(13) =536559a(14) =1480324a(15) =4084101a(16) =11267725a(17) =31086799a(18) =85766121a(19) =236622225a(20) =652822777a(21) =1801088541a(22) =4969066720a(23) =13709278307a(24) =37822859361a(25) =104350401111a(26) =287894844441a(27) =794280046581