A036374 Number of ternary rooted trees with n nodes and height at most 6.

1, 1, 1, 2, 4, 8, 17, 38, 82, 177, 376, 789, 1638, 3376, 6894, 13987, 28181, 56424, 112282, 222171, 437098, 855311, 1664755, 3223402, 6209505, 11901967, 22700056, 43083657, 81376732, 152971812, 286199220, 532954482, 987861697, 1822655134

Offset: 0

Author

N. J. A. Sloane, E. M. Rains (rains(AT)caltech.edu)

Keywords

• nonn
• fini
• full

Links

• Sean A. Irvine, Table of n, a(n) for n = 0..364
• E. M. Rains and N. J. A. Sloane, On Cayley's Enumeration of Alkanes (or 4-Valent Trees), J. Integer Sequences, Vol. 2 (1999), Article 99.1.1.
• Index entries for sequences related to rooted trees

Crossrefs

Cf. A036370.

Programs

Mathematica

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]]; A036374 = T[6] (* Jean-François Alcover, Jan 19 2016, after Alois P. Heinz (A036370) *)

Formula

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.