a(n) = binomial(5*n, n)*hypergeom([-4*n, -n], [-5*n], -1).

A331329

a(n) = binomial(5*n, n)*hypergeom([-4*n, -n], [-5*n], -1).

Terms

    a(0) =1a(1) =9a(2) =145a(3) =2625a(4) =50049a(5) =982729a(6) =19665841a(7) =398796225a(8) =8166636545a(9) =168502295625

External references