Number of Motzkin meanders of length n with an even number of humps.

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =17a(5) =40a(6) =106a(7) =307a(8) =927a(9) =2818a(10) =8480a(11) =25142a(12) =73555a(13) =213204a(14) =615074a(15) =1773036a(16) =5121195a(17) =14843518a(18) =43190084a(19) =126112096a(20) =369264395a(21) =1083378784a(22) =3182684838a(23) =9357797643a(24) =27529874201a(25) =81028448678a(26) =238599098824a(27) =702932296258