Number of up/down (or down/up) compositions of n into distinct parts.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =2a(5) =3a(6) =5a(7) =6a(8) =8a(9) =11a(10) =18a(11) =21a(12) =30a(13) =38a(14) =52a(15) =78a(16) =97a(17) =128a(18) =170a(19) =222a(20) =285a(21) =421a(22) =510a(23) =683a(24) =872a(25) =1148a(26) =1440a(27) =1893a(28) =2576a(29) =3209