a(n) = Ann(2n) where Ann(n) is the number of annular non-crossing matchings with n total endpoints.
A268042
a(n) = Ann(2n) where Ann(n) is the number of annular non-crossing matchings with n total endpoints.
Terms
- a(0) =1a(1) =3a(2) =8a(3) =20a(4) =57a(5) =166a(6) =538a(7) =1762a(8) =6045a(9) =21040a(10) =74628a(11) =267598a(12) =970134a(13) =3544416a(14) =13043650a(15) =48283236a(16) =179665425a(17) =671564330a(18) =2520312810a(19) =9492124534a(20) =35863942748a(21) =135893383596a(22) =516258841134
External references
- oeis: A268042