Number of 0..n arrays of length 3 with 0 never adjacent to n.

Terms

a(0) =2a(1) =17a(2) =50a(3) =107a(4) =194a(5) =317a(6) =482a(7) =695a(8) =962a(9) =1289a(10) =1682a(11) =2147a(12) =2690a(13) =3317a(14) =4034a(15) =4847a(16) =5762a(17) =6785a(18) =7922a(19) =9179a(20) =10562a(21) =12077a(22) =13730a(23) =15527a(24) =17474a(25) =19577a(26) =21842a(27) =24275a(28) =26882a(29) =29669