a(n) = 6^n * (1-4*n).

Terms

a(0) =1a(1) =-18a(2) =-252a(3) =-2376a(4) =-19440a(5) =-147744a(6) =-1073088a(7) =-7558272a(8) =-52068096a(9) =-352719360a(10) =-2358180864a(11) =-15600273408a(12) =-102308769792a(13) =-666095394816