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

Offset: 1

Author

Paolo P. Lava, May 27 2013

Keywords

• nonn

Examples

			For n=9962 we have:
sigma(9962)=15876 -> tau(15876)=45 -> phi(45)=24.
phi(9962)=4672 -> tau(4672)=14 -> sigma(14)=24.
		

Links

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

Crossrefs

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

Programs

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 *)