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A138154
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Numbers n such that sigma(sigma(n))-phi(phi(n)) = 2n.
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2
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OFFSET
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1,1
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COMMENTS
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No other term <10^6.
No other terms below 5*10^6 [From Jasper Mulder (jasper.mulder(AT)planet.nl), Jun 03 2010]
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LINKS
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EXAMPLE
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3193 is in the sequence because sigma(sigma(3193))-phi(phi(3193)) = sigma(3328)-phi(3060) = 7154-768 = 6386 = 2*3193.
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MAPLE
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with(numtheory): a:=proc(n) if sigma(sigma(n))-phi(phi(n))=2*n then n else end if end proc: seq(a(n), n=1..1000000);
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CROSSREFS
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KEYWORD
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more,nonn,bref
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AUTHOR
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STATUS
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approved
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