Symmetric secondary structures of RNA molecules with n nucleotides.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =2a(5) =4a(6) =5a(7) =9a(8) =12a(9) =21a(10) =29a(11) =50a(12) =71a(13) =121a(14) =175a(15) =296a(16) =434a(17) =730a(18) =1082a(19) =1812a(20) =2709a(21) =4521a(22) =6807a(23) =11328a(24) =17157a(25) =28485a(26) =43359a(27) =71844a(28) =109830a(29) =181674