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

Author

Washington Bomfim, Feb 23 2011

Keywords

• nonn

Examples

			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.
		

Links

• Wikipedia, Caterpillar tree

Crossrefs

Cf. A000055, A130131.

Formula

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