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A145748
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Numbers n such that phi(n+1)-phi(n)=sigma(n+1)-sigma(n).
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2
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2, 854, 751358, 1421637, 8775206, 8892195, 16485944, 31845344, 95494035, 277653495, 380438505, 744048855, 1091725394, 1615353002, 2284844925, 2491028745, 6345217034, 8490513014, 12784909335, 14177454885, 15669084375, 17694356295, 17836667354, 24180347115
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OFFSET
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1,1
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COMMENTS
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This sequence is a subsequence of A066198.
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LINKS
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Table of n, a(n) for n=1..24.
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MATHEMATICA
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de[n_]:=DivisorSigma[1, n]-EulerPhi[n]; Do[If[de[n]==de[n+1], Print[n]], {n, 50000000}] (* Firoozbakht *)
Select[Range[10^6], (EulerPhi[# + 1] - EulerPhi[#]) == (DivisorSigma[1, # + 1] - DivisorSigma[1, #]) &] (* Alonso del Arte, Feb 08 2012 *)
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CROSSREFS
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Cf. A066198, A145749.
Sequence in context: A214898 A028485 A034227 * A141185 A128667 A199947
Adjacent sequences: A145745 A145746 A145747 * A145749 A145750 A145751
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KEYWORD
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nonn
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AUTHOR
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Farideh Firoozbakht, Nov 01 2008
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EXTENSIONS
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a(9)-a(16) from Donovan Johnson, Dec 14 2009
a(17)-a(24) from Donovan Johnson, Feb 08 2012
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STATUS
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approved
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