Triple convolution of the three tribonacci-like sequences A000073(n), A077947(n-2), and A103143(n).

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =1a(7) =3a(8) =9a(9) =28a(10) =75a(11) =195a(12) =498a(13) =1229a(14) =2978a(15) =7115a(16) =16756a(17) =39031a(18) =90089a(19) =206228a(20) =468795a(21) =1059197a(22) =2380257a(23) =5323610a(24) =11856514a(25) =26306896a(26) =58172254a(27) =128246136a(28) =281957282a(29) =618367332