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A180963
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Numbers divisible by 3 with an odd number of 1s in their base 2 representation.
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5
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21, 42, 69, 81, 84, 87, 93, 117, 138, 162, 168, 171, 174, 186, 213, 234, 261, 273, 276, 279, 285, 309, 321, 324, 327, 333, 336, 339, 342, 345, 348, 351, 357, 369, 372, 375, 381, 405, 426, 453, 465, 468, 471, 477, 501, 522, 546, 552, 555, 558, 570, 597, 618
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OFFSET
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1,1
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COMMENTS
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Not the same as multiples of 3 with a nonzero alternating binary digit sum: a(142) = 1368, but that sequence has 1365 as the 142nd term. - Charles R Greathouse IV, Feb 06 2015
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LINKS
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FORMULA
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MATHEMATICA
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Select[3 * Range[210], OddQ[DigitCount[#, 2, 1]] &] (* Amiram Eldar, Aug 06 2023 *)
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PROG
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(PARI) isok(n) = (hammingweight(n) % 2) && (n % 3 == 0) \\ Michel Marcus, Jul 16 2013
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CROSSREFS
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KEYWORD
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nonn,easy,base
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AUTHOR
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STATUS
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approved
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