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%I #21 Oct 30 2023 10:37:43
%S 1,1,1,1,2,1,1,4,2,1,1,8,4,2,1,15,8,4,2,29,15,8,4,1,57,29,15,8,2,1,
%T 112,57,29,15,4,2,1,220,112,57,29,7,4,2
%N Irregular triangle read by rows: T(n,k) = number of Huffman-equivalence classes of ternary trees with 3n+1 leaves and 4k leaves on the bottom level (n>=1, k>=1).
%H Christian Elsholtz, Clemens Heuberger and Helmut Prodinger, <a href="https://doi.org/10.1109/TIT.2012.2226560">The number of Huffman codes, compact trees, and sums of unit fractions</a>, IEEE Trans. Information Theory, Vol. 59, No. 2, 2013 pp. 1065-1075; also arXiv:<a href="https://arxiv.org/abs/1108.5964">1108.5964</a> [math.CO], 2011.
%H Jordan Paschke, Jeffrey Burkert and Rebecca Fehribach, <a href="https://doi.org/10.1016/j.disc.2010.08.017">Computing and estimating the number of n-ary Huffman sequences of a specified length</a>, Discrete Math., 311 (2011), 1-7.
%e Triangle begins:
%e 1
%e 1
%e 1 1
%e 2 1 1
%e 4 2 1 1
%e 8 4 2 1
%e 15 8 4 2
%e 29 15 8 4 1
%e 57 29 15 8 2 1
%e 112 57 29 15 4 2 1
%e 220 112 57 29 7 4 2
%Y Cf. A176431, A176452, A194628 - A194633. Leading column gives A176503.
%K nonn,tabf,more
%O 1,5
%A _N. J. A. Sloane_, Dec 07 2010
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