A176431 - OEIS

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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).

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

2,5

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.

LINKS

Table of n, a(n) for n=2..52.

EXAMPLE

Triangle begins:

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

CROSSREFS

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

Sequence in context: A242363 A050360 A175003 * A363083 A348112 A045747

Adjacent sequences: A176428 A176429 A176430 * A176432 A176433 A176434

KEYWORD

nonn,tabf

AUTHOR

N. J. A. Sloane, Dec 07 2010

STATUS

approved