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

1,2

Links

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

Example

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

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 *)

Crossrefs

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

Sequence in context: A140184 A264854 A189948 * A025415 A371420 A307253

Adjacent sequences: A252252 A252253 A252254 * A252256 A252257 A252258

Keyword

nonn,base

Author

Paolo P. Lava, Dec 16 2014

Status

approved