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A289828 a(n) is the least k such that phi(k) = n*phi(n). 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A015126(n^2).

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

MATHEMATICA

With[{s = EulerPhi /@ Range[10^4]}, Table[First@ FirstPosition[s, n EulerPhi@ n], {n, 58}]] (* Michael De Vlieger, Aug 14 2017 *)

PROG

(PARI) a(n) = my(k=1); while(1, if(eulerphi(k)==n*eulerphi(n), return(k)); k++) \\ Felix Fröhlich, Aug 14 2017

CROSSREFS

Cf. A000010, A002618, A015126.

Sequence in context: A066044 A066460 A114221 * A226471 A175510 A144643

Adjacent sequences:  A289825 A289826 A289827 * A289829 A289830 A289831

KEYWORD

nonn,easy

AUTHOR

Altug Alkan, Aug 13 2017

STATUS

approved

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Last modified June 15 15:16 EDT 2021. Contains 345049 sequences. (Running on oeis4.)