Number of bracelets (turnover necklaces) of n beads of 2 colors, 9 of them black.

Terms

a(0) =1a(1) =1a(2) =5a(3) =12a(4) =35a(5) =79a(6) =185a(7) =375a(8) =750a(9) =1387a(10) =2494a(11) =4262a(12) =7105a(13) =11410a(14) =17930a(15) =27407a(16) =41107a(17) =60335a(18) =87154a(19) =123695a(20) =173173a(21) =238957a(22) =325845a(23) =438945a(24) =585265a(25) =772252a(26) =1009868a(27) =1308742a(28) =1682660a(29) =2146420