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A334384
Lexicographically earliest sequence of distinct positive integers such that for any n > 0, a(3*n-2), a(3*n-1) and a(3*n) are in geometric progression.
2
1, 2, 4, 3, 6, 12, 5, 10, 20, 7, 14, 28, 8, 16, 32, 9, 15, 25, 11, 22, 44, 13, 26, 52, 17, 34, 68, 18, 30, 50, 19, 38, 76, 21, 42, 84, 23, 46, 92, 24, 36, 54, 27, 45, 75, 29, 58, 116, 31, 62, 124, 33, 66, 132, 35, 70, 140, 37, 74, 148, 39, 78, 156, 40, 60, 90
OFFSET
1,2
COMMENTS
This sequence is a permutation of the natural numbers.
EXAMPLE
The first terms, alongside the corresponding common ratios, are:
n a(3*n-2) a(3*n-1) a(3*n) r
-- -------- -------- ------ ---
1 1 2 4 2
2 3 6 12 2
3 5 10 20 2
4 7 14 28 2
5 8 16 32 2
6 9 15 25 5/3
7 11 22 44 2
8 13 26 52 2
9 17 34 68 2
10 18 30 50 5/3
11 19 38 76 2
12 21 42 84 2
13 23 46 92 2
14 24 36 54 3/2
15 27 45 75 5/3
PROG
(PARI) See Links section.
CROSSREFS
Cf. A334390.
Sequence in context: A232564 A134561 A258046 * A225055 A341194 A120947
KEYWORD
nonn,look,tabf
AUTHOR
Rémy Sigrist, Apr 26 2020
STATUS
approved