A186308 Number of lobsters with n nodes that are not caterpillars.

0, 0, 0, 0, 1, 3, 11, 33, 95, 260, 696, 1816, 4659, 11795, 29520, 73267, 180485, 442157, 1077856, 2617726, 6336551, 15299287, 36857178, 88635225, 212829307, 510416549, 1222826994, 2927083468, 7001510693, 16737477645

Offset

3,6

Links

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

Wikipedia, Caterpillar tree

Formula

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

Example

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.

Crossrefs

Cf. A000055, A130131.

Sequence in context: A295626 A079996 A288038 * A352102 A171270 A182879

Adjacent sequences: A186305 A186306 A186307 * A186309 A186310 A186311

Keyword

nonn

Author

Washington Bomfim, Feb 23 2011

Status

approved