a(n) = r1^n + r2^n + r3^n where r1, r2, r3 are the three roots of x^3 - 2*x - 2 = 0.

Terms

a(0) =0a(1) =4a(2) =6a(3) =8a(4) =20a(5) =28a(6) =56a(7) =96a(8) =168a(9) =304a(10) =528a(11) =944a(12) =1664a(13) =2944a(14) =5216a(15) =9216a(16) =16320a(17) =28864a(18) =51072a(19) =90368a(20) =159872a(21) =282880a(22) =500480a(23) =885504a(24) =1566720a(25) =2771968a(26) =4904448a(27) =8677376a(28) =15352832a(29) =27163648