Number of isolated vertices in all 3-noncrossing RNA structures on n vertices.

Terms

a(0) =0a(1) =1a(2) =2a(3) =4a(4) =10a(5) =29a(6) =88a(7) =281a(8) =928a(9) =3170a(10) =11108a(11) =39844a(12) =145700a(13) =542099a(14) =2047390a(15) =7837154a(16) =30359390a(17) =118877686a(18) =470023034a(19) =1874858180a(20) =7538907394a(21) =30538466279a(22) =124544812652a(23) =511112081854