Number of valleys in all left factors of Dyck paths of length n. A valley is a (1,-1)-step followed by a (1,1)-step.
A191522
Number of valleys in all left factors of Dyck paths of length n. A valley is a (1,-1)-step followed by a (1,1)-step.
Terms
- a(0) =0a(1) =0a(2) =0a(3) =1a(4) =3a(5) =8a(6) =20a(7) =45a(8) =105a(9) =224a(10) =504a(11) =1050a(12) =2310a(13) =4752a(14) =10296a(15) =21021a(16) =45045a(17) =91520a(18) =194480a(19) =393822a(20) =831402a(21) =1679600a(22) =3527160a(23) =7113106a(24) =14872858a(25) =29953728a(26) =62403600a(27) =125550100a(28) =260757900a(29) =524190240
External references
- oeis: A191522