Number of Dyck paths of semilength n such that each level with peaks has exactly two peaks.

Terms

a(0) =1a(1) =0a(2) =1a(3) =1a(4) =2a(5) =5a(6) =15a(7) =27a(8) =76a(9) =196a(10) =548a(11) =1388a(12) =3621a(13) =9894a(14) =27553a(15) =75346a(16) =205634a(17) =563729a(18) =1565409a(19) =4370226a(20) =12191929a(21) =33980329a(22) =94874987a(23) =265668404a(24) =745652478a(25) =2095025688a(26) =5889310438a(27) =16565399257a(28) =46633521554a(29) =131388795335