Number of closed meanders with 2n crossings and 6 digons.

Terms

a(0) =2a(1) =16a(2) =110a(3) =416a(4) =1470a(5) =4128a(6) =9102a(7) =20240a(8) =40106a(9) =71312a(10) =127426a(11) =203056a(12) =336070a(13) =491392a(14) =790126a(15) =1067160a(16) =1650530a(17) =2086720a(18) =3180030a(19) =3878952a(20) =5768170a(21) =6771680a(22) =9871350a(23) =11231064a(24) =16241094a(25) =17936352a(26) =25665290a(27) =27729640a(28) =39210350a(29) =41583104