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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
OFFSET
3,6
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
Sequence in context: A295626 A079996 A288038 * A352102 A171270 A182879
KEYWORD
nonn
AUTHOR
Washington Bomfim, Feb 23 2011
STATUS
approved