Number of Motzkin meanders of length n with no level steps at odd level.

Terms

a(0) =1a(1) =2a(2) =4a(3) =9a(4) =20a(5) =47a(6) =110a(7) =264a(8) =634a(9) =1541a(10) =3754a(11) =9204a(12) =22622a(13) =55817a(14) =138026a(15) =342203a(16) =849984a(17) =2115245a(18) =5271970a(19) =13158944a(20) =32886338a(21) =82285031a(22) =206101422a(23) =516728937a(24) =1296664512a(25) =3256472235a(26) =8184526438a(27) =20584627358a(28) =51805243138a(29) =130456806425