1,2

Let Y_n be the set of trees of degree n. A nonempty subset of Y_n is called a

grove. The set of all groves of degree n is denoted by Y_n.

a(n) for n<= 7 given by right-most column of Table 1,

p.3, of Bruno and Yasaki: The arithmetic of the natural numbers N can be extended

to arithmetic operations on planar binary trees. This gives rise to a

non-commutative arithmetic theory. In this exposition, we describe this

arithmetree, first defined by Loday and investigate prime trees.

J.-L. Loday, Arithmetree, J. Algebra 258 (2002), no. 1, 275-309, Special issue in celebration of Claudio Procesi's 60th birthday.

Adriano Bruno, Dan Yasaki, The arithmetic of trees, Sep 25, 2008.

Cf. A000108.

Sequence in context: A129209 A134721 A002707 this_sequence A118913 A005042 A136582

Adjacent sequences: A144961 A144962 A144963 this_sequence A144965 A144966 A144967

nonn

Jonathan Vos Post (jvospost3(AT)gmail.com), Sep 27 2008