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Search: id:A064020
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| A064020 |
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Numbers n such that sf(n) = phi(n), where sf(n) = A013928(n). |
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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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No more terms < 30000. All terms, except the first, are multiples of 3. - Emeric Deutsch (deutsch(AT)duke.poly.edu), Jun 25 2005
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EXAMPLE
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sf(363)=220, phi(363)=220.
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MAPLE
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with(numtheory): a:=proc(n) if add(mobius(k)^2, k=1..n-1)=phi(n) then n else fi end: seq(a(n), n=1..5000); (Deutsch)
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PROGRAM
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(PARI) sf(n)=s=0; for(x=1, n, if(issquarefree(x), s++)); s; for(n=1, 10^5, if(sf(n)==eulerphi(n), print(n)))
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CROSSREFS
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Adjacent sequences: A064017 A064018 A064019 this_sequence A064021 A064022 A064023
Sequence in context: A006797 A139006 A073950 this_sequence A095412 A074428 A125052
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KEYWORD
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more,nonn
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AUTHOR
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Jason Earls (zevi_35711(AT)yahoo.com), Sep 07 2001
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EXTENSIONS
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Corrected and extended by Emeric Deutsch (deutsch(AT)duke.poly.edu), Jun 25 2005
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