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A334390 Lexicographically earliest sequence of distinct positive integers such that for any n > 0, a(n), a(2*n) and a(2*n+1) are in geometric progression. 2
1, 2, 4, 6, 18, 8, 16, 12, 24, 30, 50, 28, 98, 20, 25, 36, 108, 48, 96, 60, 120, 40, 32, 14, 7, 84, 72, 10, 5, 15, 9, 42, 49, 54, 27, 132, 363, 144, 216, 90, 135, 180, 270, 80, 160, 64, 128, 56, 224, 21, 63, 126, 189, 156, 338, 70, 490, 35, 245, 75, 375, 33 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

This sequence is a variant of A305410; here we consider geometric progressions, there arithmetic progressions.

LINKS

Rémy Sigrist, Table of n, a(n) for n = 1..6667

Rémy Sigrist, PARI program for A334390

EXAMPLE

The first terms, alongside the corresponding common ratios, are:

  n   a(n)  a(2*n)  a(2*n+1)  r

  --  ----  ------  --------  ---

   1     1       2         4    2

   2     2       6        18    3

   3     4       8        16    2

   4     6      12        24    2

   5    18      30        50  5/3

   6     8      28        98  7/2

   7    16      20        25  5/4

   8    12      36       108    3

   9    24      48        96    2

  10    30      60       120    2

PROG

(PARI) See Links section.

CROSSREFS

Cf. A305410, A334384.

Sequence in context: A294920 A046441 A192335 * A067993 A074131 A335038

Adjacent sequences:  A334387 A334388 A334389 * A334391 A334392 A334393

KEYWORD

nonn

AUTHOR

Rémy Sigrist, Apr 26 2020

STATUS

approved

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Last modified July 28 19:33 EDT 2021. Contains 346335 sequences. (Running on oeis4.)