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Search: id:A063946
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| A063946 |
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Write n in binary and complement second bit (from the left), with a(0)=0 and a(1)=1. |
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+0
1
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| 0, 1, 3, 2, 6, 7, 4, 5, 12, 13, 14, 15, 8, 9, 10, 11, 24, 25, 26, 27, 28, 29, 30, 31, 16, 17, 18, 19, 20, 21, 22, 23, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 96, 97, 98, 99, 100, 101, 102
(list; graph; listen)
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OFFSET
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0,3
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FORMULA
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If 2*2^k<=n<3*2^k then a(n)=n+2^k; if 3*2^k<=n<4*2^k then a(n)=n-2^k.
a(0)=0, a(1)=1, a(2)=3, a(3) = 2, a(2n) = 2a(n), a(2n+1) = 2a(n) + 1. - Ralf Stephan (ralf(AT)ark.in-berlin.de), Aug 23 2003
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EXAMPLE
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a(11)=15 since 11 is written in binary as 1011 which changes to 1111 i.e. 15; a(12)=8 since 12 is written as 1100 which changes to 1000 i.e. 8.
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PROGRAM
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(PARI) a(n)=if(n<2, n>0, 3/2*2^floor(log(n)/log(2))-2^floor(log(4/3*n)/log(2))+n) (from R. Stephan)
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CROSSREFS
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Cf. A004442, A053645, A054429.
Sequence in context: A125764 A023897 A100527 this_sequence A120231 A083362 A003188
Adjacent sequences: A063943 A063944 A063945 this_sequence A063947 A063948 A063949
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KEYWORD
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easy,nonn
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AUTHOR
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Henry Bottomley (se16(AT)btinternet.com), Sep 03 2001
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