OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..100
EXAMPLE
Arithmetic derivative of 26 is 15, phi(15) = 8 and 8' = 12 that is equal to phi(26).
MAPLE
with(numtheory):P:=proc(q) local a, b, n, p;
for n from 1 to q do a:=phi(n*add(op(2, p)/op(1, p), p=ifactors(n)[2]));
b:=a*add(op(2, p)/op(1, p), p=ifactors(a)[2]);
if phi(n)=b then print(n); fi; od; end: P(10^9);
MATHEMATICA
f[n_] := If[Abs@ n < 2, 0, n Total[#2/#1 & @@@ FactorInteger@ Abs@ n]]; Select[Range@ 100000, f@ EulerPhi@ f@ # == EulerPhi@ # &] (* Michael De Vlieger, Aug 07 2015, after Michael Somos at A003415 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Paolo P. Lava, Aug 06 2015
STATUS
approved