

A194630


Arises in enumerating Huffman codes, compact trees, and sums of unit fractions.


3



1, 1, 1, 2, 4, 8, 16, 32, 64, 127, 253, 505, 1008, 2012, 4016, 8016, 16000, 31936, 63744, 127234, 253961, 506910, 1011800, 2019568, 4031088, 8046112, 16060160, 32056322, 63984903, 127714833, 254920736, 508825640, 1015623664, 2027200176
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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) <= 7*p(k+1). [Joerg Arndt, Dec 18 2012]
Row 6 of Table 1 of Elsholtz, row 1 being A002572, row 2 being A176485, row 3 being A176503, row 4 being A194628, and row 5 being A194629.


LINKS

Table of n, a(n) for n=1..34.
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=7 */


CROSSREFS

Cf. A002572, A176485, A176503, A194628, A194629.
Sequence in context: A239560 A066178 A122189 * A251672 A251747 A251761
Adjacent sequences: A194627 A194628 A194629 * A194631 A194632 A194633


KEYWORD

nonn


AUTHOR

Jonathan Vos Post, Aug 30 2011


EXTENSIONS

Added terms beyond a(20)=127234, Joerg Arndt, Dec 18 2012.


STATUS

approved



