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A045740 Number of components in all forests on nodes on a circle. 0
1, 3, 12, 62, 370, 2397, 16345, 115376, 834786, 6152285, 45990120, 347673108, 2652283517, 20385035972, 157656007680, 1225743120520, 9572972899946, 75056029550721, 590469939950716, 4659115833115680, 36859770507695688 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..21.

FORMULA

Sum(k*binomial(n, k-1)*binomial(3*n-2*k-1, n-k)/(2*n-k), k=1..n)

CROSSREFS

Sequence in context: A038171 A258798 A074516 * A187820 A074529 A143916

Adjacent sequences:  A045737 A045738 A045739 * A045741 A045742 A045743

KEYWORD

nonn

AUTHOR

Emeric Deutsch

STATUS

approved

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Last modified January 20 02:05 EST 2019. Contains 319320 sequences. (Running on oeis4.)