Sum of the trapezoid weights of all peakless Motzkin paths of length n (n>=0).

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =3a(5) =8a(6) =20a(7) =49a(8) =119a(9) =291a(10) =715a(11) =1768a(12) =4396a(13) =10983a(14) =27551a(15) =69351a(16) =175081a(17) =443119a(18) =1123963a(19) =2856383a(20) =7271377a(21) =18538391a(22) =47327615a(23) =120972510a(24) =309555666a(25) =792917565a(26) =2032905981a(27) =5216436109a(28) =13395813003a(29) =34425270629