A066463 - OEIS

A066463

Numbers n such that phi(sigma(phi(n))) = phi(n).

1, 2, 3, 4, 6, 13, 15, 16, 20, 21, 24, 26, 28, 30, 36, 42, 241, 255, 256, 272, 287, 305, 320, 325, 340, 369, 384, 385, 408, 429, 465, 480, 482, 488, 495, 496, 510, 525, 572, 574, 610, 616, 620, 650, 700, 732, 738, 744, 770, 779, 792, 793, 803, 858, 900, 905

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Harry J. Smith, Table of n, a(n) for n = 1..1000

MATHEMATICA

Select[Range[1, 10^3], EulerPhi[DivisorSigma[1, EulerPhi[ # ]]] == EulerPhi[ # ] &]

PROG

(PARI) { n=0; for (m=1, 10^10, if (eulerphi(sigma(eulerphi(m))) == eulerphi(m), write("b066463.txt", n++, " ", m); if (n==1000, return)) ) } \\ Harry J. Smith, Feb 16 2010

CROSSREFS

Sequence in context: A274694 A352580 A096988 * A073146 A038767 A363198

Adjacent sequences: A066460 A066461 A066462 * A066464 A066465 A066466

KEYWORD

nonn

AUTHOR

Joseph L. Pe, Jan 02 2002

STATUS

approved