a(n) = Sum_{k=1..n} Catalan(k)^2.

Terms

a(0) =1a(1) =5a(2) =30a(3) =226a(4) =1990a(5) =19414a(6) =203455a(7) =2248355a(8) =25887399a(9) =307993015a(10) =3763786811a(11) =47032778955a(12) =598933188955