Number of compositions of n in which no part is unique (every part appears at least twice).

Terms

a(0) =1a(1) =0a(2) =1a(3) =1a(4) =2a(5) =1a(6) =9a(7) =11a(8) =34a(9) =53a(10) =108a(11) =169a(12) =400a(13) =680a(14) =1530a(15) =2984a(16) =6362a(17) =12498a(18) =25766a(19) =50093a(20) =102126a(21) =199309a(22) =400288a(23) =788227a(24) =1581584a(25) =3135117a(26) =6286310a(27) =12532861a(28) =25121292a(29) =50184582