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A092586
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Numbers n such that sigma[phi(n)]-phi[sigma(n)] is nonzero and is divisible by (n+1), that is A065395[n]/(n+1)=phi[sigma(n)]-sigma[phi(n)]/(n+1) is a nonzero integer.
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0
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7, 87, 231, 463, 617, 691, 751, 855, 1059, 1127, 2795, 4819, 11999, 18527, 22481, 75311, 121939, 232901, 256751, 288883, 313919, 371519, 845831, 1285841, 1762799, 1815167, 7195199, 9096191, 40324121, 93070943, 99388823, 113140151
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OFFSET
| 1,1
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EXAMPLE
| sigma(phi(x))-phi(sigma(x))/phi(x+1) equals 1 if x=7; is 2 if x=463; is 3 if x=4819.
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MATHEMATICA
| f[ x_] := EulerPhi[ DivisorSigma[1, x]] - DivisorSigma[1, EulerPhi[x]]; t = {}; Do[ s = f[n]; If[ s != 0 && Mod[ s, n + 1] == 0, Print[n]; AppendTo[t, n], {n, 2*10^8}]; t
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CROSSREFS
| Cf. A033632, A092584-A092588, A000203, A000010, A065395.
Sequence in context: A000686 A102923 A196257 * A048363 A183613 A173812
Adjacent sequences: A092583 A092584 A092585 * A092587 A092588 A092589
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Mar 01 2004
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EXTENSIONS
| Edited and extended by Robert G. Wilson v Mar 03 2004
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