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A248381 Multiples of 3 in A247665 in order of appearance. 2
9, 15, 27, 57, 81, 177, 243, 393, 579, 729, 849, 1257, 2187, 4197, 4143, 5853, 6561, 17817, 17781, 19683, 56157, 59049, 104289, 104277, 154509 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The initial multiples of 3 occur at positions 6,13,28,57,115,231, ... - conjecturally, for n > 13, A247665(n) is a multiple of 3 iff n = 29*2^k-1, k >= 0.

LINKS

Table of n, a(n) for n=1..25.

EXAMPLE

Table showing index where multiples of 3 appear, the multiple of 3, and the number of different prime factors of that term:

6 9 1

13 15 2

28 27 1

57 57 2

115 81 1

231 177 2

463 243 1

927 393 2

1855 579 2

3711 729 1

7423 849 2

14847 1257 2

29695 2187 1

59391 4197 2

118783 4143 2

237567 5853 2

475135 6561 1

950271 17817 2

1900543 17781 2

3801087 19683 1

7602175 56157 2

15204351 59049 1

30408703 104289 2

60817407 104277 2

121634815 154509 2

CROSSREFS

Cf. A247665, A248379 (multiples of 2).

Sequence in context: A258813 A046353 A046356 * A060874 A147511 A124580

Adjacent sequences:  A248378 A248379 A248380 * A248382 A248383 A248384

KEYWORD

nonn,more

AUTHOR

Russ Cox and N. J. A. Sloane, Oct 12 2014

STATUS

approved

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Last modified November 16 21:47 EST 2018. Contains 317275 sequences. (Running on oeis4.)