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Search: id:A092587
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| A092587 |
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Numbers n such that sigma[phi(n)]-phi[sigma(n)] is nonzero and is divisible by phi(n), that is A065395[n]/A000010[n]= phi[sigma(n)]-sigma[phi(n)]/phi(n) is a nonzero integer. |
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+0
1
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| 2, 18, 21, 99, 133, 151, 175, 183, 350, 366, 449, 450, 477, 532, 581, 645, 702, 843, 1072, 1253, 1346, 1508, 1645, 1833, 2085, 2097, 2150, 2421, 3668, 3950, 4223, 4312, 4453, 5264, 6601, 6853, 7128, 7423, 7622, 7713, 8325, 9028, 9364, 9707, 10820
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OFFSET
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1,1
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EXAMPLE
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sigma(phi(x))-phi(sigma(x))/phi(x) equals -3 for x=450; -2 at x=18; -1 at x=2; 1 for x=21; 2 at x=99; 3 for x=4223.
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MATHEMATICA
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fs[x_] := EulerPhi[DivisorSigma[1, x]] sf[x_] := DivisorSigma[1, EulerPhi[x]] {t=Table[0, {60}], j=1}; Do[s=(sf[n]-fs[n])/EulerPhi[n]; If[ !Equal[s, 0]&&IntegerQ[s], Print[n]; t[[j]]=n; j=j+1], {n, 2, 1000000}] t
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CROSSREFS
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Cf. A033632, A092584-A092588, A000203, A000010, A065395.
Sequence in context: A076378 A066242 A022371 this_sequence A015787 A063430 A031104
Adjacent sequences: A092584 A092585 A092586 this_sequence A092588 A092589 A092590
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Mar 01 2004
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