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

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =6a(6) =19a(7) =57a(8) =162a(9) =442a(10) =1176a(11) =3092a(12) =8119a(13) =21451a(14) =57275a(15) =154771a(16) =422970a(17) =1166762a(18) =3241282a(19) =9049682a(20) =25356109a(21) =71229481a(22) =200520398a(23) =565594404a(24) =1598436567a(25) =4526347791a(26) =12843234665a(27) =36514629469a(28) =104015020498a(29) =296835850798