a(n+3) = a(n+2) + a(n+1) + a(n) - 4.

Terms

a(0) =0a(1) =0a(2) =8a(3) =4a(4) =8a(5) =16a(6) =24a(7) =44a(8) =80a(9) =144a(10) =264a(11) =484a(12) =888a(13) =1632a(14) =3000a(15) =5516a(16) =10144a(17) =18656a(18) =34312a(19) =63108a(20) =116072a(21) =213488a(22) =392664a(23) =722220a(24) =1328368a(25) =2443248a(26) =4493832a(27) =8265444a(28) =15202520a(29) =27961792