Number of horizontal steps in all peak and valleyless Motzkin meanders of length n.

Terms

a(0) =0a(1) =1a(2) =4a(3) =13a(4) =39a(5) =110a(6) =300a(7) =801a(8) =2106a(9) =5473a(10) =14097a(11) =36056a(12) =91697a(13) =232108a(14) =585212a(15) =1470557a(16) =3684682a(17) =9209417a(18) =22967446a(19) =57167993a(20) =142051519a(21) =352427720a(22) =873157093a(23) =2160579740a(24) =5340150100a(25) =13185150903a(26) =32523933395a(27) =80156852042a(28) =197391001215a(29) =485723767342