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

Author

Andrew Howroyd, Dec 04 2020

Keywords

• nonn

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

Crossrefs

Cf. A000081.

Column 4 of A339303.

Formula

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