A339524 Number of unordered pairs of rooted trees with a total of n nodes and an even total of leaves.

0, 1, 1, 2, 3, 8, 18, 49, 120, 313, 802, 2120, 5591, 14942, 40033, 108108, 293094, 798839, 2185341, 6002085, 16538599, 45716952, 126727195, 352215812, 981268481, 2739930091, 7666333161, 21491833976, 60358490615, 169798048026, 478420333601

Offset: 1

Author

Washington Bomfim, Dec 08 2020

Keywords

• nonn

Comments

Equivalently, the number of rooted trees on n+1 nodes, where the root has degree 2, and the number of leaves is even.

Links

• Washington Bomfim, Illustration of initial terms
• Index entries for sequences related to rooted trees

Crossrefs

Cf. A027852, A339525.

Formula

a(n) = A027852(n) - A339525(n).