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A190640 Numbers whose base-3 expansion ends in 2 and does not contain any 1's. 2
2, 8, 20, 26, 56, 62, 74, 80, 164, 170, 182, 188, 218, 224, 236, 242, 488, 494, 506, 512, 542, 548, 560, 566, 650, 656, 668, 674, 704, 710, 722, 728, 1460, 1466, 1478, 1484, 1514, 1520, 1532, 1538, 1622, 1628, 1640, 1646, 1676, 1682, 1694, 1700, 1946, 1952, 1964, 1970, 2000, 2006, 2018, 2024, 2108, 2114, 2126 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
Conjecture: a(n) = A055246(n) + 1. - Michel Marcus, Aug 24 2016
a(n) = A005823(2n). - Charles R Greathouse IV, Aug 24 2016
MATHEMATICA
Select[Range[2200], Last[IntegerDigits[#, 3]]==2&&DigitCount[#, 3, 1]==0&] (* Harvey P. Dale, Sep 09 2012 *)
FromDigits[#, 3]&/@(Join[#, {2}]&/@Tuples[{0, 2}, 7]) (* Harvey P. Dale, Jul 25 2020 *)
PROG
(PARI) is(n)=n%3==2 && setsearch(Set(digits(n, 3)), 1)==0 \\ Charles R Greathouse IV, Aug 24 2016
(PARI) a(n)=2*fromdigits(binary(2*n-1), 3) \\ Charles R Greathouse IV, Aug 24 2016
CROSSREFS
Subsequence of A005823.
Cf. A005836.
Sequence in context: A108180 A233571 A192153 * A230434 A018226 A162626
KEYWORD
nonn,base,easy
AUTHOR
N. J. A. Sloane, May 15 2011
STATUS
approved

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Last modified April 22 08:40 EDT 2024. Contains 371893 sequences. (Running on oeis4.)