A252255 Numbers n such that sigma(Rev(phi(n))) = phi(Rev(sigma(n))), where sigma is the sum of divisors and phi the Euler totient function.

1, 14, 61, 966, 1428, 9174, 15642, 19934, 22155, 27075, 36650, 48731, 51095, 54184, 57902, 59711, 61039, 89276, 98645, 113080, 126850, 140283, 142149, 154670, 165822, 190908, 197705, 198712, 202096, 203107, 247268, 274368, 274716, 307836, 311925, 331037, 366740

Offset: 1

Author

Paolo P. Lava, Dec 16 2014

Keywords

• nonn
• base

Examples

			phi(14) = 6, Rev(6) = 6 and sigma(6) = 12;
sigma(14) = 24, Rev(24) = 42 and sigma(42) = 12.
		

Links

• Paolo P. Lava, Table of n, a(n) for n = 1..100

Crossrefs

Cf. A000010, A000203, A069225, A070835, A070856.

Programs

Maple

with(numtheory): T:=proc(w) local x, y, z; x:=0; y:=w;
for z from 1 to ilog10(w)+1 do x:=10*x+(y mod 10); y:=trunc(y/10); od; x; end:
P:=proc(q) local a, b, k; global n; for n from 1 to q do
if sigma(T(phi(n)))=phi(T(sigma(n))) then print(n); fi; od; end: P(10^12);

Mathematica

Select[Range[400000],DivisorSigma[1,IntegerReverse[EulerPhi[#]]] == EulerPhi[ IntegerReverse[ DivisorSigma[ 1,#]]]&] (* Requires Mathematica version 10 or later *)  (* Harvey P. Dale, Apr 15 2017 *)