Number of Schroeder paths of semilength n up to reversal.

Terms

a(0) =1a(1) =2a(2) =5a(3) =15a(4) =54a(5) =216a(6) =947a(7) =4375a(8) =21018a(9) =103550a(10) =520041a(11) =2649391a(12) =13655190a(13) =71053780a(14) =372727751a(15) =1968880111a(16) =10463765490a(17) =55909445082a(18) =300160457453