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A226384
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Numbers k such that rad(phi(k)) = phi(rad(k)).
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3
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1, 2, 3, 6, 7, 11, 12, 14, 22, 23, 24, 28, 31, 43, 44, 46, 47, 48, 56, 59, 62, 67, 71, 79, 83, 86, 88, 92, 94, 96, 103, 107, 112, 118, 124, 131, 134, 139, 142, 158, 166, 167, 172, 176, 179, 184, 188, 191, 192, 206, 211, 214, 223, 224, 227, 236, 239, 248, 262
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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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MAPLE
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with(numtheory):
rad:= n-> mul(i, i=factorset(n)):
a:= proc(n) option remember; local k; for k from 1+a(n-1)
while phi(rad(k))<>rad(phi(k)) do od; k
end: a(0):=0:
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MATHEMATICA
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rad[n_] := Product[fa[n][[i, 1]], {i,
Length[fa[n]]}]; fa = FactorInteger;
Select[Range[500], rad[EulerPhi[#]] == EulerPhi[rad[#]] &]
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PROG
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(PARI) is(n)=my(f=factor(n)); lcm(factor(eulerphi(f))[, 1])==prod(i=1, #f~, f[i, 1]-1) \\ Charles R Greathouse IV, Nov 13 2013
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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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