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A339302 Number of unlabeled rooted trees with n nodes rooted at two indistinguishable nodes at distance 3 from each other. 2
1, 2, 8, 22, 69, 194, 564, 1584, 4484, 12550, 35204, 98412, 275422, 770416, 2157334, 6044684, 16956389, 47614380, 133865184, 376789710, 1061822884, 2995785714, 8461975888, 23928712708, 67739408492, 191964821890, 544559201634, 1546306248630, 4394984617389 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,2

COMMENTS

Number of unoriented linear forests with n nodes and 4 rooted trees.

LINKS

Andrew Howroyd, Table of n, a(n) for n = 4..500

FORMULA

G.f.: (r(x)^4 + r(x^2)^2)/2 where r(x) is the g.f. of A000081.

CROSSREFS

Cf. A000081.

Column 4 of A339303.

Sequence in context: A321573 A137103 A089586 * A045695 A106053 A121135

Adjacent sequences:  A339299 A339300 A339301 * A339303 A339304 A339305

KEYWORD

nonn

AUTHOR

Andrew Howroyd, Dec 04 2020

STATUS

approved

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Last modified January 17 23:09 EST 2021. Contains 340249 sequences. (Running on oeis4.)