a(2n) = Cat(n), a(2n+1) = 3*Cat(n), where Cat(n) = binomial(2n,n)/(n+1) are the Catalan numbers (A000108).

A126324

a(2n) = Cat(n), a(2n+1) = 3*Cat(n), where Cat(n) = binomial(2n,n)/(n+1) are the Catalan numbers (A000108).

Terms

    a(0) =1a(1) =3a(2) =1a(3) =3a(4) =2a(5) =6a(6) =5a(7) =15a(8) =14a(9) =42a(10) =42a(11) =126a(12) =132a(13) =396a(14) =429a(15) =1287a(16) =1430a(17) =4290a(18) =4862a(19) =14586a(20) =16796a(21) =50388a(22) =58786a(23) =176358a(24) =208012a(25) =624036a(26) =742900a(27) =2228700a(28) =2674440a(29) =8023320

External references