a(n) = (2*n+1) * (2*n)! / (sqrt(4*(n+1)*Product_{k=1..2*n+1} lcm(k, 2*n+2-k))).

Terms

a(0) =1a(1) =1a(2) =2a(3) =12a(4) =4a(5) =8a(6) =72a(7) =160a(8) =16a(9) =3456a(10) =32a(11) =1792a(12) =129600a(13) =1024a(14) =128a(15) =1492992a(16) =256a(17) =2048000a(18) =18289152a(19) =180224a(20) =1024a(21) =573308928a(22) =1280000a(23) =1703936a(24) =241864704a(25) =719323136a(26) =8192a(28) =16384a(29) =33554432a(30) =234125033472