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A176431 Irregular triangle read by rows: T(n,k) = number of Huffman-equivalence classes of binary trees with n leaves and 2k leaves on the bottom level (n>=2, k>=1).

%I A176431 #15 Mar 30 2012 16:51:57
%S A176431 1,1,1,1,2,1,3,2,5,3,1,9,5,1,1,16,9,2,1,28,16,4,2,50,28,7,4,89,50,12,
%T A176431 7,1,159,89,22,12,2,1,285,159,39,22,3,2,510,285,70,39,22,3,1
%N A176431 Irregular triangle read by rows: T(n,k) = number of Huffman-equivalence classes of binary trees with n leaves and 2k leaves on the bottom level (n>=2, k>=1).
%D A176431 J. Paschke et al., Computing and estimating the number of n-ary Huffman sequences of a specified length, Discrete Math., 311 (2011), 1-7.
%e A176431 Triangle begins:
%e A176431 1
%e A176431 1
%e A176431 1 1
%e A176431 2 1
%e A176431 3 2
%e A176431 5 3 1
%e A176431 9 5 1 1
%e A176431 16 9 2 1
%e A176431 28 16 4 2
%e A176431 50 28 7 4
%e A176431 89 50 12 7 1
%e A176431 159 89 22 12 2 1
%e A176431 285 159 39 22 3 2
%e A176431 510 285 70 39 22 3 1
%Y A176431 Cf. A176452, A176463. First three columns are A002572 (twice), A002573.
%K A176431 nonn,tabf
%O A176431 2,5
%A A176431 _N. J. A. Sloane_, Dec 07 2010