Prime alternating tangle types (of knots) with n crossings.

Terms

a(0) =1a(1) =2a(2) =4a(3) =10a(4) =29a(5) =98a(6) =372a(7) =1538a(8) =6755a(9) =30996a(10) =146982a(11) =715120a(12) =3552254a(13) =17951322a(14) =92045058a(15) =477882876a(16) =2508122859a(17) =13289437362a(18) =71010166670a(19) =382291606570