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A194632 Arises in enumerating Huffman codes, compact trees, and sums of unit fractions. 1
1, 1, 1, 2, 4, 8, 16, 32, 64, 128, 256, 511, 1021, 2041, 4080, 8156, 16304, 32592, 65152, 130240, 260352, 520448, 1040384, 2079746, 4157449, 8310814, 16613464, 33210608, 66388592, 132711968, 265293568, 530326528, 1060132096, 2119222786, 4236363783, 8468566033 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

a(n+1) is the number of compositions n=p(1)+p(2)+...+p(m) with p(1)=1 and p(k) <= 9*p(k+1).  [Joerg Arndt, Dec 18 2012]

Row 8 of Table 1 of Elsholtz, row 1 being A002572, row 2 being A176485, row 3 being A176503, row 4 being A194628, row 5 being A194629, row 6 being  A194630, and row 7 being A194631.

LINKS

Table of n, a(n) for n=1..36.

Christian Elsholtz, Clemens Heuberger, Helmut Prodinger, The number of Huffman codes, compact trees, and sums of unit fractions, arXiv:1108.5964v1 [math.CO], Aug 30, 2011.

PROG

(PARI) /* see A002572, set t=9 */

CROSSREFS

Cf. A002572, A176485, A176503, A194628, A194629, A194630, A194631.

Sequence in context: A172318 A234590 A104144 * A123464 A113019 A069877

Adjacent sequences:  A194629 A194630 A194631 * A194633 A194634 A194635

KEYWORD

nonn

AUTHOR

Jonathan Vos Post, Aug 30 2011

EXTENSIONS

Added terms beyond a(20)=130240, Joerg Arndt, Dec 18 2012.

STATUS

approved

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Last modified April 20 05:52 EDT 2014. Contains 240779 sequences.