Number of closed meander systems of order n+1 with n components.

Terms

a(0) =2a(1) =12a(2) =56a(3) =240a(4) =990a(5) =4004a(6) =16016a(7) =63648a(8) =251940a(9) =994840a(10) =3922512a(11) =15452320a(12) =60843510a(13) =239519700a(14) =942871200a(15) =3711935040a(16) =14615744220a(17) =57562286760a(18) =226760523600a(19) =893550621600