Triangle read by rows: number of hex trees with n edges and k branches of length 1 (0<=k<=n).

Terms

a(0) =1a(1) =0a(2) =3a(3) =9a(4) =0a(5) =1a(6) =27a(7) =6a(8) =0a(9) =3a(10) =90a(11) =18a(12) =27a(13) =0a(14) =2a(15) =297a(16) =135a(17) =81a(18) =24a(19) =0a(20) =6a(21) =1053a(22) =648a(23) =351a(24) =72a(25) =90a(26) =0a(27) =5a(28) =3888a(29) =2889