Number of skeins with 2n+1 edges.

Terms

a(0) =1a(1) =1a(2) =4a(3) =15a(4) =62a(5) =271a(6) =1247a(7) =5938a(8) =29113a(9) =145815a(10) =743384a(11) =3844314a(12) =20118681a(13) =106348391a(14) =567002169a(15) =3045455865a(16) =16463622763a(17) =89509216860a(18) =489103356753