a(n) = 2*binomial(5*n+1,n)/(4*n+2).

Terms

a(0) =1a(1) =2a(2) =11a(3) =80a(4) =665a(5) =5980a(6) =56637a(7) =556512a(8) =5620485a(9) =57985070a(10) =608462470a(11) =6474009360a(12) =69682358811a(13) =757366074080