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Search: id:A071008
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| A071008 |
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Numbers n such that uphi(uphi(n))=n/2. |
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+0
1
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OFFSET
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1,1
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COMMENT
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If n=Product p_i^r_i then uphi(n)=Product ( p_i^r_i-1); for example uphi(12)=(4-1)*(3-1)=6
If 2^n+1 is a Fermat prime then 2^(2*n) is a solution of the equation.
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EXAMPLE
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Factorizations: 2, 2^2, 2^4. 2^8, 2^16, 2^9*3^5*5^2, 2^32
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CROSSREFS
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Cf. A030163.
Sequence in context: A050472 A109457 A105788 this_sequence A001146 A114641 A152690
Adjacent sequences: A071005 A071006 A071007 this_sequence A071009 A071010 A071011
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KEYWORD
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nonn
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AUTHOR
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Yasutoshi Kohmoto (zbi74583(AT)boat.zero.ad.jp)
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