a(n) = Sum_{k=0..n} k^3 * (-1)^k * 3^(n-k) * binomial(n,k).

Terms

a(0) =0a(1) =-1a(2) =2a(3) =18a(4) =64a(5) =160a(6) =288a(7) =224a(8) =-1024a(9) =-6912a(10) =-28160a(11) =-95744a(12) =-294912a(13) =-851968a(14) =-2351104a(15) =-6266880a(16) =-16252928a(17) =-41222144a(18) =-102629376a(19) =-251527168a(20) =-608174080a(21) =-1453326336a(22) =-3437232128a(23) =-8055160832a(24) =-18723373056a(25) =-43201331200a(26) =-99019128832a(27) =-225586446336