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A066462 Numbers n such that phi(sigma(phi(n))) = sigma(n). 1
1, 5, 221, 763, 2759, 11303, 12749, 13079, 20677, 33725, 42253, 75101, 96193, 140225, 160369, 168113, 171667, 195889, 227099, 229969, 269161, 275971, 316129, 344317, 385033, 387163, 392677, 437999, 498253, 528209, 562913, 611381, 661181 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Harry J. Smith, Table of n, a(n) for n = 1..771

MATHEMATICA

Select[Range[1, 10^6], EulerPhi[DivisorSigma[1, EulerPhi[ # ]]] == DivisorSigma[1, # ] &]

PROG

(PARI) { n=0; for (m=1, 10^9, if (eulerphi(sigma(eulerphi(m))) == sigma(m), write("b066462.txt", n++, " ", m); if (n==1000, return)) ) } \\ Harry J. Smith, Feb 16 2010

CROSSREFS

Sequence in context: A024070 A290179 A050617 * A046193 A195633 A112999

Adjacent sequences:  A066459 A066460 A066461 * A066463 A066464 A066465

KEYWORD

nonn

AUTHOR

Joseph L. Pe, Jan 02 2002

STATUS

approved

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Last modified October 23 17:20 EDT 2018. Contains 316529 sequences. (Running on oeis4.)