a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3), n > 3, with a(0)=a(1)=a(2)=0, a(3)=1.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =4a(5) =10a(6) =20a(7) =36a(8) =64a(9) =120a(10) =240a(11) =496a(12) =1024a(13) =2080a(14) =4160a(15) =8256a(16) =16384a(17) =32640a(18) =65280a(19) =130816a(20) =262144a(21) =524800a(22) =1049600a(23) =2098176a(24) =4194304a(25) =8386560a(26) =16773120a(27) =33550336a(28) =67108864a(29) =134225920