Number of compositions of n such that two adjacent parts are not equal modulo 3.

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =4a(5) =5a(6) =13a(7) =17a(8) =23a(9) =54a(10) =75a(11) =106a(12) =224a(13) =329a(14) =482a(15) =942a(16) =1436a(17) =2163a(18) =4004a(19) =6255a(20) =9619a(21) =17144a(22) =27220a(23) =42513a(24) =73785a(25) =118402a(26) =187082a(27) =318715a(28) =514958a(29) =820744