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 A063470 Numbers n such that tau(n)*4 = phi(n). 9
 34, 45, 52, 102, 140, 156, 252, 360, 420 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Phi(n) = k*tau(n) has at most finitely many solutions for any constant k or even for slowly increasing functions like k(n) = n^(epsilon). - Labos Elemer, Jul 20 2001 For n > 2, tau(n) > 2 and phi(n) <= n-1 so the least solution a(1) to tau(n)*k = phi(n), must be a(1) >= 2*k+1, for the case k=4, a(1) >= 2*4+1 = 9. - Enrique Pérez Herrero, May 12 2012 LINKS FORMULA a(1) = A175667(4) a(A112954(4)) = A112955(4). - Enrique Pérez Herrero, May 12 2012. PROG (PARI) for(n=1, 10^6, if(numdiv(n)*4==eulerphi(n), print(n))) CROSSREFS Cf. A062516. Cf. A112954, A020488, A063469. Sequence in context: A248527 A206262 A302457 * A089715 A327132 A260284 Adjacent sequences:  A063467 A063468 A063469 * A063471 A063472 A063473 KEYWORD fini,nonn,full AUTHOR Jason Earls, Jul 26 2001 EXTENSIONS "full" keyword from Max Alekseyev, Mar 01 2010 STATUS approved

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Last modified December 8 16:34 EST 2021. Contains 349596 sequences. (Running on oeis4.)