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Search: id:A137469
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| A137469 |
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Numbers with an odd number of 1's in base 5 expansion. |
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+0
3
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| 1, 5, 7, 8, 9, 11, 16, 21, 25, 27, 28, 29, 31, 35, 37, 38, 39, 40, 42, 43, 44, 45, 47, 48, 49, 51, 55, 57, 58, 59, 61, 66, 71, 76, 80, 82, 83, 84, 86, 91, 96, 101, 105, 107, 108, 109, 111, 116, 121, 125, 127, 128, 129, 131, 135, 137, 138, 139, 140, 142, 143, 144, 145
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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This is to A000069 (Odious numbers: odd number of 1's in binary expansion) as A007091 (Numbers in base 5) is to A007088 (Numbers written in base 2). Note that odd number of 1's in base 3 expansion is simply the odd numbers.
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EXAMPLE
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a(18) = 40 (base 10) is in the sequence because 40 (base 10) = 130 (base 5) which has an odd number (1) of 1's ; whereas 41 is not in the sequence because 41 (base 10) = 131 (base 5) has an even number (2) of 1's.
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MAPLE
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isA137469 := proc(n) local a, d ; a := 0 ; for d in convert(n, base, 5) do if d =1 then a := a+1 ; fi ; od; RETURN( a mod 2 = 1 ) ; end: for n from 1 to 400 do if isA137469(n) then printf("%d, ", n) ; fi ; od: - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 21 2008
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MATHEMATICA
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Select[Range[200], OddQ[DigitCount[ #, 5][[1]]] &] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Apr 21 2008
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CROSSREFS
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Cf. A000069, A007088, A007091.
Sequence in context: A122904 A104693 A031221 this_sequence A043353 A023726 A080644
Adjacent sequences: A137466 A137467 A137468 this_sequence A137470 A137471 A137472
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KEYWORD
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base,easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), Apr 20 2008
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl) and Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Apr 21 2008
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