Number of (2n+1)-node rooted trees of height n.

Terms

a(0) =1a(1) =1a(2) =4a(3) =18a(4) =93a(5) =498a(6) =2744a(7) =15349a(8) =86802a(9) =494769a(10) =2837412a(11) =16351036a(12) =94599339a(13) =549118128a(14) =3196397701a(15) =18651028188a(16) =109057492901a(17) =638863803720