Factorial codes for the fixed points of the square of Vaillé's 1997 bijection on Dyck paths.

Terms

a(0) =0a(1) =1a(2) =11a(3) =21a(4) =111a(5) =321a(6) =1111a(7) =4321a(8) =11111a(9) =23211a(10) =54321a(11) =111111a(12) =122211a(13) =324321a(14) =654321a(15) =1111111a(16) =1222121a(17) =2432211a(18) =3244321a(19) =7654321a(20) =11111111a(21) =22121321a(22) =34443211a(23) =87654321a(24) =111111111a(25) =122322121a(26) =325543321a(27) =987654321a(28) =1111111111