A378078 Number of noncrossing trees with n edges and all nodes having degree at most 3.
1, 1, 3, 12, 50, 219, 987, 4552, 21366, 101730, 490094, 2384520, 11699844, 57825103, 287611755, 1438536144, 7230782414, 36506547918, 185047345050, 941359362760, 4804468999932, 24593960996814, 126239765780606, 649610643221616, 3350542070046300, 17318377059738820
Offset: 0
Keywords
Examples
a(4) = A001764(4) - 5 where the 5 trees excluded are those with one node connected to the other four.
Links
- Andrew Howroyd, Table of n, a(n) for n = 0..500
Programs
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PARI
seq(n)={my(g=serreverse(x/(1+2*x+3*x^2) + O(x*x^n))); Vec(1 + g + g^2 + g^3)}
Formula
G.f.: (1 + g(x) + g(x)^2 + g(x)^3) where g(x)/x is the g.f. of A122871.