A066465 Numbers k such that sigma(phi(sigma(k))) = phi(k).

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

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) isok(k) = { sigma(eulerphi(sigma(k))) == eulerphi(k) } \\ 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