Number of compositions of n with no part greater than 3 such that no two adjacent parts are equal.

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =3a(5) =4a(6) =8a(7) =9a(8) =12a(9) =21a(10) =27a(11) =37a(12) =58a(13) =78a(14) =109a(15) =164a(16) =227a(17) =319a(18) =467a(19) =656a(20) =928a(21) =1341a(22) =1896a(23) =2689a(24) =3859a(25) =5477a(26) =7782a(27) =11126a(28) =15817a(29) =22496