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 A066465 Numbers n such that sigma(phi(sigma(n))) = phi(n). 1
 1, 13, 43, 97, 211, 533, 1133, 2627, 3907, 4687, 4801, 11231, 15689, 33613, 45995, 82643, 92543, 106571, 143903, 156383, 159947, 173239, 190399, 370913, 390247, 393049, 437747, 487547, 513193, 519601, 577633, 616399, 715163, 740213, 883387 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Harry J. Smith, Table of n, a(n) for n = 1..650 MATHEMATICA Select[Range[1, 10^6], DivisorSigma[1, EulerPhi[DivisorSigma[1, # ]]] == EulerPhi[ # ] &] PROG (PARI) { n=0; for (m=1, 10^10, if (sigma(eulerphi(sigma(m))) == eulerphi(m), write("b066465.txt", n++, " ", m); if (n==1000, return)) ) } \\ Harry J. Smith, Feb 17 2010 CROSSREFS Sequence in context: A187677 A082040 A106734 * A023262 A067260 A135241 Adjacent sequences: A066462 A066463 A066464 * A066466 A066467 A066468 KEYWORD nonn AUTHOR Joseph L. Pe, Jan 02 2002 STATUS approved

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Last modified August 11 23:45 EDT 2024. Contains 375082 sequences. (Running on oeis4.)