A176431 - OEIS

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 #15 Mar 30 2012 16:51:57

%S 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 7,1,159,89,22,12,2,1,285,159,39,22,3,2,510,285,70,39,22,3,1

%N 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 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 Triangle begins:

%e 1

%e 1 1

%e 2 1

%e 3 2

%e 5 3 1

%e 9 5 1 1

%e 16 9 2 1

%e 28 16 4 2

%e 50 28 7 4

%e 89 50 12 7 1

%e 159 89 22 12 2 1

%e 285 159 39 22 3 2

%e 510 285 70 39 22 3 1

%Y Cf. A176452, A176463. First three columns are A002572 (twice), A002573.

%K nonn,tabf

%O 2,5

%A _N. J. A. Sloane_, Dec 07 2010