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A228519 Numbers n such that sigma(n) = sigma(n - phi(n)), where sigma(n) is the sum of divisors of n and phi(n) is the Euler totient function of n.

%I A228519 #33 Oct 11 2019 16:54:02
%S A228519 9356,52412,110442,160834,220884,266866,289230,321668,420790,441768,
%T A228519 533732,556818,578460,643336,731530,841580,883536,1067464,1113636,
%U A228519 1156920,1286672,1446150,1463060,1683160,1767072,2103950,2134928,2227272,2313840,2545888,2573344,2892300
%N A228519 Numbers n such that sigma(n) = sigma(n - phi(n)), where sigma(n) is the sum of divisors of n and phi(n) is the Euler totient function of n.
%H A228519 Amiram Eldar, <a href="/A228519/b228519.txt">Table of n, a(n) for n = 1..1000</a>
%F A228519 sigma(9356- phi(9356)) = sigma(9356 - 4676) = 16380 = sigma(9356).
%p A228519 with(numtheory); P:=proc(q) local n; for n from 1 to q do
%p A228519 if sigma(n)=sigma(n-phi(n)) then print(n); fi; od; end: P(10^9);
%t A228519 Select[Range[10^6], DivisorSigma[1, #] == DivisorSigma[1, # - EulerPhi@ #] &] (* _Michael De Vlieger_, Jun 21 2016 *)
%Y A228519 Cf. A000010, A000203, A051953, A067880.
%K A228519 nonn,easy
%O A228519 1,1
%A A228519 _Paolo P. Lava_, Jun 21 2016