a(n) = binomial(6*n, 2*n) / (4*n + 1).

A235534

a(n) = binomial(6*n, 2*n) / (4*n + 1).

Terms

    a(0) =1a(1) =3a(2) =55a(3) =1428a(4) =43263a(5) =1430715a(6) =50067108a(7) =1822766520a(8) =68328754959

External references