Triangle of coefficients of generating function of 4-ary rooted trees of height at most n.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =1a(7) =1a(8) =1a(9) =1a(10) =1a(11) =1a(12) =2a(13) =3a(14) =5a(15) =6a(16) =8a(17) =9a(18) =11a(19) =11a(20) =12a(21) =11a(22) =11a(23) =9a(24) =8a(25) =6a(26) =5a(27) =3a(28) =2a(29) =1