a(n) = (12*n + 3)^3.

Terms

a(0) =27a(1) =3375a(2) =19683a(3) =59319a(4) =132651a(5) =250047a(6) =421875a(7) =658503a(8) =970299a(9) =1367631a(10) =1860867a(11) =2460375a(12) =3176523a(13) =4019679a(14) =5000211a(15) =6128487a(16) =7414875a(17) =8869743a(18) =10503459a(19) =12326391a(20) =14348907a(21) =16581375a(22) =19034163a(23) =21717639a(24) =24642171a(25) =27818127a(26) =31255875a(27) =34965783a(28) =38958219a(29) =43243551