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 A136132 Integral values of (sigma(sigma(n))-phi(phi(n)))/n (the corresponding values of n are given in A136131). 3
 0, 2, 2, 3, 3, 3, 5, 3, 5, 3, 5, 4, 8, 8, 6, 5, 2, 8, 6, 8, 10, 8, 8, 6, 8, 8, 3, 8, 6, 8, 6, 5, 12, 8, 6, 8, 10, 3, 6, 8, 8, 8, 10, 6, 6, 5, 8, 8, 14, 13, 3, 12, 8, 5, 8, 12, 8, 6, 8, 8, 16, 8, 12, 11, 15, 10, 5, 9, 6, 8, 16, 6, 12, 12, 8, 8, 10, 16 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Donovan Johnson, Table of n, a(n) for n = 1..92 EXAMPLE The first 5 in the sequence corresponds to n = 92; indeed, (sigma(sigma(92))-phi(phi(92)))/92 = (sigma(168)-phi(44))/92 = (480-20)/92 = 5. MAPLE with(numtheory): a:=proc(n) if type((sigma(sigma(n))-phi(phi(n)))/n, integer) =true then (sigma(sigma(n))-phi(phi(n)))/n else end if end proc: seq(a(n), n= 1..1000000); PROG (PARI) { for(n=1, 10000000, ss=sigma(sigma(n))-eulerphi(eulerphi(n)) ; if(ss%n==0, print(ss/n) ; ) ; ) ; } - R. J. Mathar, Mar 07 2008 CROSSREFS Cf. A136131, A138154, A137600. Sequence in context: A300888 A300944 A301498 * A136545 A125843 A210957 Adjacent sequences: A136129 A136130 A136131 * A136133 A136134 A136135 KEYWORD nonn AUTHOR Emeric Deutsch, Mar 03 2008 EXTENSIONS More terms from R. J. Mathar, Mar 07 2008 STATUS approved

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Last modified July 22 00:58 EDT 2024. Contains 374478 sequences. (Running on oeis4.)