A226118 - OEIS

A226118

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

1, 2, 136, 160, 170, 204, 240, 282, 716, 745, 1002, 1077, 1465, 1509, 1578, 1868, 2012, 2157, 2346, 2720, 2760, 3608, 3898, 4101, 4461, 4512, 5066, 5322, 5898, 6189, 7080, 7185, 7341, 7628, 7660, 8108, 8517, 8665, 8698, 8709, 8805, 8922, 8940, 9234, 9745, 9962

(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=9962 we have:

sigma(9962)=15876 -> tau(15876)=45 -> phi(45)=24.

phi(9962)=4672 -> tau(4672)=14 -> sigma(14)=24.

MAPLE

with(numtheory); A226118:=proc(q) local n;

for n from 1 to q do

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

fi; od; end: A226118(10^6);

MATHEMATICA

Select[Range[10000], EulerPhi[DivisorSigma[0, DivisorSigma[1, #]]] == DivisorSigma[ 1, DivisorSigma[ 0, EulerPhi[#]]]&] (* Harvey P. Dale, May 26 2016 *)

CROSSREFS

Cf. A000005, A000010, A000203, A033632, A067160, A076361, A226117, A226119.

Sequence in context: A097641 A065963 A353012 * A216030 A216083 A000662

Adjacent sequences: A226115 A226116 A226117 * A226119 A226120 A226121

KEYWORD

nonn

AUTHOR

Paolo P. Lava, May 27 2013

STATUS

approved