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 A064020 Numbers n such that sf(n) = phi(n), where sf(n) = A013928(n). 0
 2, 3, 9, 33, 363, 1089, 1653, 3237, 4297761, 32348343651 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS No more terms < 30000. All terms, except the first, are multiples of 3. - Emeric Deutsch, Jun 25 2005 a(11) > 5*10^10. - Donovan Johnson, Jun 10 2011 No other terms < 10^12. - Jud McCranie, Aug 27 2013 LINKS EXAMPLE sf(363) = 220, phi(363) = 220. MAPLE 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); # Emeric Deutsch, Jun 25 2005 PROG (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))) CROSSREFS Sequence in context: A277345 A259943 A296263 * A204442 A306523 A095412 Adjacent sequences:  A064017 A064018 A064019 * A064021 A064022 A064023 KEYWORD more,nonn AUTHOR Jason Earls, Sep 07 2001 EXTENSIONS Corrected and extended by Emeric Deutsch, Jun 25 2005 a(9) from Donovan Johnson, Jul 15 2009 a(10) from Donovan Johnson, Jun 10 2011 STATUS approved

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Last modified June 2 08:00 EDT 2020. Contains 334767 sequences. (Running on oeis4.)