a(n) = (8*n + 1)^3.

Terms

a(0) =1a(1) =729a(2) =4913a(3) =15625a(4) =35937a(5) =68921a(6) =117649a(7) =185193a(8) =274625a(9) =389017a(10) =531441a(11) =704969a(12) =912673a(13) =1157625a(14) =1442897a(15) =1771561a(16) =2146689a(17) =2571353a(18) =3048625a(19) =3581577a(20) =4173281a(21) =4826809a(22) =5545233a(23) =6331625a(24) =7189057