G.f.: hypergeom([1/12, 5/12, 7/12, 11/12], [1/6, 1/2, 5/6], 1728*x).
a(n) = a(n-1)*6*(12*n - 1)*(12*n - 5)*(12*n - 7)*(12*n - 11)/(n*(2*n - 1)*(6*n - 1)*(6*n - 5)). -
Neven Sajko, Jul 22 2023
a(n) = binomial(12*n,6*n)*binomial(2*n,n)/binomial(4*n,n) = binomial(12*n,6*n)*binomial(5*n,n)/binomial(5*n,2*n). -
Chai Wah Wu, Feb 15 2026