

A300669


Positive numbers k with two consecutive ones in the binary representation of 1/k.


2



5, 9, 10, 11, 13, 17, 18, 19, 20, 21, 22, 23, 25, 26, 27, 29, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 49, 50, 52, 53, 54, 55, 57, 58, 59, 61, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89
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OFFSET

1,1


COMMENTS

Equivalently, these are the numbers k such that A300655(k) > 1.
Equivalently, these are the numbers k such that A300653(k, 3) = 3.
If n belongs to this sequence then 2*n belongs to this sequence.
This sequence has similarities with A004780; here 1/k has two consecutive ones in binary, there k has two consecutive ones in binary.
See A300630 for the complementary sequence.


LINKS

Table of n, a(n) for n=1..66.


EXAMPLE

The first terms, alongside the binary representation of 1/a(n), are:
n a(n) bin(1/a(n)) with repeating digits in parentheses
  
1 5 0.(0011)
2 9 0.(0001110)
3 10 0.0(0011)
4 11 0.(0001011101)
5 13 0.0(00100111011)
6 17 0.(00001111)
7 18 0.0(000111)
8 19 0.(000011010111100101)
9 20 0.00(0011)
10 21 0.(000011)


PROG

(PARI) is(n) = my (f=1/max(2, n), s=Set()); while (!setsearch(s, f), if (floor(f*4)==3, return (1), s=setunion(s, Set(f)); f=frac(f*2))); return (0)


CROSSREFS

Cf. A004780, A300653, A300655, A300630 (complement).
Sequence in context: A187713 A101082 A277706 * A166934 A257739 A094695
Adjacent sequences: A300666 A300667 A300668 * A300670 A300671 A300672


KEYWORD

nonn,base


AUTHOR

Rémy Sigrist, Mar 11 2018


STATUS

approved



