Number of compositions of n into 4 parts such that no two adjacent parts are equal.

Terms

a(0) =2a(1) =6a(2) =14a(3) =24a(4) =46a(5) =66a(6) =100a(7) =138a(8) =192a(9) =246a(10) =324a(11) =402a(12) =506a(13) =612a(14) =746a(15) =882a(16) =1054a(17) =1224a(18) =1432a(19) =1644a(20) =1896a(21) =2148a(22) =2448a(23) =2748a(24) =3098a(25) =3450a(26) =3854a(27) =4260a(28) =4726a(29) =5190