Number of Motzkin excursions of length n with an even number of humps and an even number of peaks.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =4a(6) =11a(7) =31a(8) =86a(9) =230a(10) =608a(11) =1588a(12) =4151a(13) =10925a(14) =29083a(15) =78373a(16) =213702a(17) =588366a(18) =1631906a(19) =4550346a(20) =12736029a(21) =35746763a(22) =100561622a(23) =283486702a(24) =800798659a(25) =2266802139a(26) =6429960961a(27) =18276530005a(28) =52051825058a(29) =148520257620