A226117 - OEIS

A226117

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

1, 3, 4, 5, 14, 17, 20, 21, 22, 26, 51, 63, 65, 66, 72, 76, 80, 84, 90, 100, 106, 112, 132, 135, 150, 152, 165, 182, 190, 196, 221, 222, 232, 246, 255, 290, 291, 292, 294, 320, 326, 375, 386, 396, 424, 450, 460, 489, 530, 561, 567, 585, 588, 600, 606, 608, 615

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

OFFSET

1,2

LINKS

Paolo P. Lava, Table of n, a(n) for n = 1..1000

EXAMPLE

For n=23529 we have:

phi(23529)=13200 -> sigma(13200)=46128 -> tau(46128)=30.

tau(23529)=16 -> sigma(16)=31 -> phi(31)=30.

MAPLE

with(numtheory); A226117:=proc(q) local n;

for n from 1 to q do

if phi(sigma(tau(n)))=tau(sigma(phi(n))) then print(n);

fi; od; end: A226117(10^6);

MATHEMATICA

Select[Range[700], EulerPhi[DivisorSigma[1, DivisorSigma[0, #]]] == DivisorSigma[ 0, DivisorSigma[ 1, EulerPhi[ #]]]&] (* Harvey P. Dale, Dec 12 2021 *)

CROSSREFS

Cf. A000005, A000010, A000203, A033632, A067160, A076361, A226118, A226119.

Sequence in context: A211518 A049895 A365017 * A221173 A346599 A330138

Adjacent sequences: A226114 A226115 A226116 * A226118 A226119 A226120

KEYWORD

nonn

AUTHOR

Paolo P. Lava, May 27 2013

STATUS

approved