A378079 Number of series-reduced noncrossing trees with n edges.
1, 1, 0, 4, 5, 33, 91, 408, 1485, 6195, 24838, 103752, 432796, 1834140, 7815900, 33591376, 145197017, 631281591, 2757917260, 12102728740, 53321334381, 235768155073, 1045889996047, 4653534540816, 20761857325000, 92862669150004, 416316199107096, 1870414803490240
Offset: 0
Keywords
Examples
The a(3) = 4 trees are:
o---o o---o o o o o
| \ / | | / \ |
o o o o o---o o---o
Links
- Andrew Howroyd, Table of n, a(n) for n = 0..500
Programs
-
PARI
seq(n)={my(g=serreverse(x/(1/(1-x)^2 - 2*x) + O(x*x^n))); Vec(1/(1 - g) - g^2)}
Formula
G.f.: 1/(1 - g(x)) - g(x)^2 where g(x) is the g.f. of A030980.