a(n) = (1 - (-11)^n)/12.

Terms

a(0) =1a(1) =-10a(2) =111a(3) =-1220a(4) =13421a(5) =-147630a(6) =1623931a(7) =-17863240a(8) =196495641a(9) =-2161452050a(10) =23775972551a(11) =-261535698060