Number of Motzkin excursions of length n with an even number of humps and without peaks.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =2a(7) =6a(8) =19a(9) =57a(10) =161a(11) =433a(12) =1122a(13) =2826a(14) =6968a(15) =16916a(16) =40630a(17) =96958a(18) =230732a(19) =549278a(20) =1311473a(21) =3146659a(22) =7596281a(23) =18460921a(24) =45163078a(25) =111164142a(26) =275067208a(27) =683577528a(28) =1704485046a(29) =4260677154