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Search: id:A130913
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| A130913 |
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Composite solutions to the equation phi(x)+sigma(x)=2*reversal(x). |
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1
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OFFSET
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1,1
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COMMENT
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For a prime p we have phi(p)+sigma(p)=2*reversal(p) iff p is a palindrome.
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EXAMPLE
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485700768 is in the sequence because 485700768 is composite and phi(485700768)+sigma(485700768)=1734015168=2*867007584.
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CROSSREFS
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Cf. A130000.
Sequence in context: A017636 A139029 A049360 this_sequence A087534 A112444 A083630
Adjacent sequences: A130910 A130911 A130912 this_sequence A130914 A130915 A130916
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KEYWORD
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hard,more,nonn
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AUTHOR
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Farideh Firoozbakht (mymontain(AT)yahoo.com), Jun 09 2007
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