a(n) = binomial(2n, n)^2.

Terms

a(0) =1a(1) =4a(2) =36a(3) =400a(4) =4900a(5) =63504a(6) =853776a(7) =11778624a(8) =165636900a(9) =2363904400a(10) =34134779536a(11) =497634306624