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A220160
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Numbers n for which phi(n) = phi(n-1) - phi(n+1).
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3
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194, 3530, 9338, 27230, 46794, 78182, 90194, 112994, 135014, 437184, 849404, 935220, 1078580, 1283600, 1986974, 2209584, 2341184, 2411174, 2689694, 2744144, 3619070, 3712544, 4738184, 5132984, 6596120, 7829030, 8184714, 12176108, 12292004, 13342958, 26400842
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OFFSET
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1,1
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LINKS
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EXAMPLE
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phi(3529) - phi(3531) = 3528 - 2120 = 1408 = phi(3530).
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MATHEMATICA
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Select[Range[10^6], EulerPhi[#] == EulerPhi[# - 1] - EulerPhi[# + 1] &]
With[{ep=EulerPhi[Range[27500000]]}, Flatten[Position[Partition[ ep, 3, 1], _?(#[[1]]- #[[3]]==#[[2]]&), {1}, Heads->False]]]+1 (* Harvey P. Dale, Feb 04 2015 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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