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A289828
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a(n) is the least k such that phi(k) = n*phi(n).
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2
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1, 3, 7, 15, 25, 13, 43, 51, 81, 41, 121, 65, 157, 129, 143, 255, 289, 109, 361, 187, 301, 253, 529, 193, 625, 313, 487, 337, 841, 241, 961, 771, 661, 685, 899, 433, 1369, 1083, 937, 641, 1681, 551, 1849, 881, 1147, 1013, 2209, 769, 2401, 1111, 1751, 1249, 2809, 1141, 2323, 1469, 2053, 1711
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OFFSET
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1,2
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LINKS
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FORMULA
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n^2/log log n << a(n) <= n^2. More specifically (on the lower bound), a(n) > n^2(e^-gamma + o(1))/log log n. - Charles R Greathouse IV, Aug 14 2017
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MATHEMATICA
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With[{s = EulerPhi /@ Range[10^4]}, Table[First@ FirstPosition[s, n EulerPhi@ n], {n, 58}]] (* Michael De Vlieger, Aug 14 2017 *)
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PROG
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(PARI) a(n) = my(k=1); while(1, if(eulerphi(k)==n*eulerphi(n), return(k)); k++) \\ Felix Fröhlich, Aug 14 2017
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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