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Search: id:A162215
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| A162215 |
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a(n) = the smallest multiple of n that is > 2n and contains the same number of 1's in its binary representation as n contains. |
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1
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| 4, 8, 9, 16, 20, 18, 21, 32, 36, 40, 44, 36, 52, 42, 45, 64, 68, 72, 76, 80, 84, 88, 92, 72, 100, 104, 108, 84, 116, 90, 93, 128, 132, 136, 140, 144, 148, 152, 156, 160, 164, 168, 172, 176, 135, 184, 188, 144, 196, 200, 153, 208, 212, 216, 220, 168, 228, 232, 236
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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a(n) = 3n only if n is in sequence A077459. Otherwise, a(n) = 4n.
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EXAMPLE
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15 in binary is 1111, which contains four 1's as binary digits. 15*3 = 45, which is 101101 in binary. This also contains four 1's. So, a(15) = 3*15 = 45.
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MAPLE
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A000120 := proc(n) add(d, d=convert(n, base, 2)) ; end: A162215 := proc(n) local k; for k from 3 do if A000120(k*n)= A000120(n) then RETURN(k*n) ; fi; od: end: seq(A162215(n), n=1..80) ; [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 04 2009]
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CROSSREFS
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A077459
Sequence in context: A069265 A003679 A079432 this_sequence A134344 A119315 A010390
Adjacent sequences: A162212 A162213 A162214 this_sequence A162216 A162217 A162218
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KEYWORD
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base,nonn
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AUTHOR
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Leroy Quet (q1qq2qqq3qqqq(AT)yahoo.com), Jun 28 2009
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EXTENSIONS
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a(4) corrected and sequence extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 04 2009
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