Number of ladders in all peakless Motzkin paths of length n (n>=0).

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =3a(5) =7a(6) =19a(7) =50a(8) =129a(9) =334a(10) =862a(11) =2220a(12) =5715a(13) =14706a(14) =37836a(15) =97353a(16) =250535a(17) =644905a(18) =1660558a(19) =4277165a(20) =11020698a(21) =28406449a(22) =73245390a(23) =188928736a(24) =487492213a(25) =1258305122a(26) =3248994414a(27) =8391747865a(28) =21681628237a(29) =56035444491