a(n) = (4*n+3)^3.

Terms

a(0) =27a(1) =343a(2) =1331a(3) =3375a(4) =6859a(5) =12167a(6) =19683a(7) =29791a(8) =42875a(9) =59319a(10) =79507a(11) =103823a(12) =132651a(13) =166375a(14) =205379a(15) =250047a(16) =300763a(17) =357911a(18) =421875a(19) =493039a(20) =571787a(21) =658503a(22) =753571a(23) =857375a(24) =970299a(25) =1092727a(26) =1225043