3,6

Table of n, a(n) for n=3..32.

Wikipedia, Caterpillar tree

a(n) = A130131(n) - (2^(n-4) + 2^[(n-4)/2]).

All the trees of order less than 7 are caterpillars. Only one tree with 7 nodes is a lobster and is not a caterpillar, so a(3)=a(4)=a(5)=a(6)=0, and a(7)=1.

Cf. A000055, A130131.

Sequence in context: A295626 A079996 A288038 * A171270 A182879 A124640

Adjacent sequences: A186305 A186306 A186307 * A186309 A186310 A186311

nonn

Washington Bomfim, Feb 23 2011

approved