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Search: id:A136132
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| A136132 |
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Integral values of [sigma(sigma(n))-phi(phi(n))]/n (the corresponding values of n are given in A136131). |
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3
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| 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
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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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.
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MAPLE
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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);
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PROGRAM
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(PARI) { for(n=1, 10000000, ss=sigma(sigma(n))-eulerphi(eulerphi(n)) ; if(ss%n==0, print(ss/n) ; ) ; ) ; } - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Mar 07 2008
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CROSSREFS
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Cf. A136131, A138154, A137600.
Adjacent sequences: A136129 A136130 A136131 this_sequence A136133 A136134 A136135
Sequence in context: A110868 A110869 A110876 this_sequence A136545 A125843 A147665
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KEYWORD
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more,nonn
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AUTHOR
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Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 03 2008
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Mar 07 2008
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