a(n) = 12^n - n^3.

Terms

a(0) =1a(1) =11a(2) =136a(3) =1701a(4) =20672a(5) =248707a(6) =2985768a(7) =35831465a(8) =429981184a(9) =5159779623a(10) =61917363224a(11) =743008369357