a(n) = Sum_{j=0..11} n^j.

Terms

a(0) =1a(1) =12a(2) =4095a(3) =265720a(4) =5592405a(5) =61035156a(6) =435356467a(7) =2306881200a(8) =9817068105a(9) =35303692060a(10) =111111111111a(11) =313842837672a(12) =810554586205