a(n) = T(2n,n+4), T given by A027948.

Terms

a(0) =1a(1) =10a(2) =231a(3) =2300a(4) =14820a(5) =72905a(6) =298925a(7) =1077748a(8) =3540913a(9) =10871723a(10) =31775031a(11) =89633545a(12) =246575109a(13) =666605513a(14) =1781049298a(15) =4721874921a(16) =12456394685a(17) =32758238316a(18) =85985810716a(19) =225446971141a(20) =590714939822