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A062236
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Sum of the levels of all nodes in all noncrossing trees with n edges.
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2
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1, 8, 58, 408, 2831, 19496, 133638, 913200, 6226591, 42387168, 288194424, 1957583712, 13286865060, 90126841064, 611029568078, 4140789069408, 28050809681679, 189964288098632, 1286119453570746, 8705397371980728
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OFFSET
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1,2
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LINKS
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Emeric Deutsch and M. Noy, New statistics on non-crossing trees, in: Formal Power Series and Algebraic Combinatorics (Proceedings of the 12th International Conference, FPSAC'00, Moscow, Russia, 2000), pp. 667-676, Springer, Berlin, 2000.
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FORMULA
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G.f.: g*(g-1)/(3-2*g)^2, where function g=g(x) satisfies g=1+xg^3, and can be expressed as g(x) = 2*sin(arcsin(3*sqrt(3*x)/2)/3)/sqrt(3*x). [Corrected by Max Alekseyev, Oct 27 2022]
g(x) = Sum_{n >= 0} binomial(3*n,n) / (2*n+1) * x^n. - Max Alekseyev, Oct 27 2022
Recurrence: 8*n*(2*n-1)*a(n) = 6*(36*n^2-45*n+10)*a(n-1) - 81*(3*n-5)*(3*n-1)*a(n-2). - Vaclav Kotesovec, Oct 13 2012
a(n) = 2^(n-2)*(3*n-1)*hypergeometric([-3*n, 1-n, -n+4/3], [-n, -n+1/3], -1/2). The a(n) are values of the polynomials A358091. - Peter Luschny, Oct 28 2022
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MAPLE
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a := n -> add(2^(n-2-i)*(n-i)*(3*n-3*i-1)*binomial(3*n, i), i=0..n-1)/n;
A062236 := n -> 2^(n-2)*(3*n-1)*hypergeom([-3*n, 1-n, -n+4/3], [-n, -n+1/3], -1/2):
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MATHEMATICA
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Table[Sum[2^(n-2-k)*(n-k)*(3*n-3*k-1)*Binomial[3*n, k], {k, 0, n-1}]/n, {n, 1, 20}] (* Vaclav Kotesovec, Oct 13 2012 *)
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PROG
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(PARI) { for (n=1, 200, a=sum(i=0, n-1, 2^(n-2-i)*(n-i)*(3*n-3*i-1)*binomial(3*n, i))/n; write("b062236.txt", n, " ", a) ) } \\ Harry J. Smith, Aug 03 2009
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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