Alternating sum of Motzkin numbers A001006.

Terms

a(0) =1a(1) =0a(2) =2a(3) =2a(4) =7a(5) =14a(6) =37a(7) =90a(8) =233a(9) =602a(10) =1586a(11) =4212a(12) =11299a(13) =30536a(14) =83098a(15) =227474a(16) =625993a(17) =1730786a(18) =4805596a(19) =13393688a(20) =37458331a(21) =105089228a(22) =295673995a(23) =834086420a(24) =2358641377a(25) =6684761124a(26) =18985057352a(27) =54022715450a(28) =154000562759a(29) =439742222070