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A167768
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First of 4 or more consecutive integers with equal values of phi(phi(n)).
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2
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OFFSET
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1,2
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COMMENTS
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LINKS
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EXAMPLE
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p2(1) = p2(2) = p2(3) = p2(4) = 1, p2(7) = p2(8) = p2(9) = p2(10) = 2.
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MATHEMATICA
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a[n_] := EulerPhi[EulerPhi[n]]; Select[Range[10000], a[#] == a[# + 1] && a[# + 1] == a[# + 2] && a[# + 2] == a[# + 3] &] (* G. C. Greubel, Jun 23 2016 *)
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PROG
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(PARI) pp(n) = eulerphi(eulerphi(n))
isA167768(n) = pp(n)==pp(n+1) && pp(n+1)==pp(n+2) && pp(n+2)==pp(n+3) \\ Michael B. Porter, Nov 24 2009
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CROSSREFS
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KEYWORD
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more,nonn,hard
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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