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).

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

Offset: 2

Author

N. J. A. Sloane, Dec 07 2010

Keywords

• nonn
• tabf

Examples

			Triangle begins:
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 7 1
159 89 22 12 2 1
285 159 39 22 3 2
510 285 70 39 22 3 1
		

References

• J. Paschke et al., Computing and estimating the number of n-ary Huffman sequences of a specified length, Discrete Math., 311 (2011), 1-7.

Crossrefs

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