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 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 (list; graph; refs; listen; history; text; internal format)
 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 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

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Last modified March 19 00:03 EDT 2019. Contains 321305 sequences. (Running on oeis4.)