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A288849
Number of distinct rational numbers that can be obtained in n steps by a straight-line program (SLP) starting at 1 using addition, subtraction, multiplication and division.
3
1, 3, 7, 21, 83, 484, 4084, 49479
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OFFSET
0,2
LINKS
Table of n, a(n) for n=0..7.
EXAMPLE
The sets of numbers obtainable at the n-th step are:
S(0) = { 1 },
S(1) = { 0, 1, 2 },
S(2) = { -1, 0, 1/2, 1, 2, 3, 4 },
S(3) = { -3, -2, -3/2, -1, -1/2, 0, 1/4, 1/3, 1/2, 2/3, 1, 3/2, 2, 5/2, 3, 4, 5, 6, 8, 9, 16 }.
CROSSREFS
Cf.
A214872
,
A288759
,
A288850
.
A216999
provides the corresponding results if division is not used.
Sequence in context:
A319123
A173794
A049365
*
A031885
A259202
A169981
Adjacent sequences:
A288846
A288847
A288848
*
A288850
A288851
A288852
KEYWORD
nonn
,
hard
,
more
AUTHOR
Hugo Pfoertner
, Jun 18 2017
EXTENSIONS
a(7) from
Alois P. Heinz
, Jun 18 2017
STATUS
approved
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Last modified April 25 12:15 EDT 2024. Contains 371969 sequences. (Running on oeis4.)