a(n) = 2*(4*n+1)!/(3*n+2)!.A370056a(n) = 2*(4*n+1)!/(3*n+2)!.Terms a(0) =1a(1) =2a(2) =18a(3) =312a(4) =8160a(5) =287280a(6) =12751200a(7) =684028800a(8) =43062243840External referencesoeis: A370056