OFFSET
1,2
COMMENTS
A051674 is a subsequence of this sequence.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..147
EXAMPLE
The arithmetic derivative of 508 is 512, phi(508) = 252, phi(512) = 256 and 508 - 252 = 512 - 256 = 256, so 508 is a term.
MAPLE
with(numtheory); P:=proc(q) local a, n, p;
for n from 1 to q do a:=n*add(op(2, p)/op(1, p), p=ifactors(n)[2]);
if phi(a)-a=phi(n)-n then print(n); fi;
od; end: P(10^9);
MATHEMATICA
d[1] = 0; d[n_] := n*Total[#2/#1 & @@@ FactorInteger[n]]; p[n_] := EulerPhi[n] - n; seqQ[n_] := p[d[n]] == p[n]; Select[Range[100000], seqQ] (* Amiram Eldar, Mar 31 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Paolo P. Lava, Mar 31 2014
EXTENSIONS
More terms from Amiram Eldar, Mar 31 2019
STATUS
approved