Number of subwords of the form UDDD in nondecreasing Dyck paths of length 2*n.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =5a(5) =19a(6) =64a(7) =202a(8) =612a(9) =1803a(10) =5206a(11) =14809a(12) =41650a(13) =116114a(14) =321478a(15) =885169a(16) =2426462a(17) =6627499a(18) =18048088a(19) =49026874a(20) =132901176a(21) =359625015a(22) =971639014a(23) =2621683741a(24) =7065545950a(25) =19022080034a(26) =51163908874a(27) =137499581917a(28) =369235213742a(29) =990822728623