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A186308 Number of lobsters with n nodes that are not caterpillars. 1
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 (list; graph; refs; listen; history; text; internal format)
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 * A171270 A182879 A124640

Adjacent sequences:  A186305 A186306 A186307 * A186309 A186310 A186311

KEYWORD

nonn

AUTHOR

Washington Bomfim, Feb 23 2011

STATUS

approved

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Last modified January 23 12:51 EST 2022. Contains 350511 sequences. (Running on oeis4.)