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A045739 Number of edges in all noncrossing forests on n nodes on a circle. 2
1, 9, 70, 535, 4101, 31633, 245512, 1915875, 15020545, 118231212, 933812892, 7397179309, 58746824150, 467602683135, 3729318261224, 29795160492299, 238421091129957, 1910544426355420, 15329353155160880, 123138401704273620 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

LINKS

Andrew Howroyd, Table of n, a(n) for n = 2..200

FORMULA

a(n) = Sum_{k=1..n-1} k*binomial(n, k+1)*binomial(n+2*k-1, k)/(n+k).

a(n) = Sum_{k=1..n-1} k*A094040(n, k). - Andrew Howroyd, Nov 17 2017

PROG

(PARI) a(n) = sum(k=1, n-1, k*binomial(n, k+1)*binomial(n+2*k-1, k)/(n+k)); \\ Andrew Howroyd, Nov 12 2017

CROSSREFS

Cf. A094040.

Sequence in context: A167534 A110202 A110201 * A098205 A000899 A226013

Adjacent sequences:  A045736 A045737 A045738 * A045740 A045741 A045742

KEYWORD

nonn

AUTHOR

Emeric Deutsch

STATUS

approved

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Last modified January 22 18:06 EST 2019. Contains 319365 sequences. (Running on oeis4.)