A036373 - OEIS

%I #19 Oct 29 2020 03:26:53

%S 1,1,1,2,4,8,16,33,63,121,225,415,749,1344,2365,4129,7106,12104,20354,

%T 33883,55706,90628,145729,231801,364555,567206,872727,1328545,2000536,

%U 2980554,4393287,6407683,9246830,13204526,18657905,26088244

%N Number of ternary rooted trees with n nodes and height at most 5.

%H Sean A. Irvine, <a href="/A036373/b036373.txt">Table of n, a(n) for n = 0..121</a>

%H <a href="/index/Ro#rooted">Index entries for sequences related to rooted trees</a>

%F If T_i(z) = g.f. for ternary trees of height at most i, T_{i+1}(z)=1+z*(T_i(z)^3/6+T_i(z^2)*T_i(z)/2+T_i(z^3)/3); T_0(z) = 1.

%t T[0] = {1}; T[n_] := T[n] = Module[{f, g}, f[z_] := Sum[T[n - 1][[i]]*z^(i - 1), {i, 1, Length[T[n - 1]]}]; g = 1 + z*(f[z]^3/6 + f[z^2]*f[z]/2 + f[z^3]/3); CoefficientList[g, z]]; A036373 = T[5] (* _Jean-François Alcover_, Jan 19 2016, after _Alois P. Heinz_ (A036370) *)

%Y Cf. A036370.

%K nonn,fini,full

%O 0,4

%A _N. J. A. Sloane_, E. M. Rains (rains(AT)caltech.edu)