A339302 Number of unlabeled rooted trees with n nodes rooted at two indistinguishable nodes at distance 3 from each other.

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

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