%I
%S 5,11,19,71,247,271,991,2232,6200,8271,10295,16744,18496,18576,25704,
%T 26656,102175,122607,166624,225939,301103,747967,7237384,7302592,
%U 15760224,21770800,28121184,72967087,98617024,104577848,173859007,253496176,335610184,371191600
%N Numbers n such that uphi(n)*usigma(n) = uphi(n+1)*usigma(n+1), where uphi is the unitary totient function (A047994) and usigma the sum of unitary divisors (A034448).
%C The unitary version of A244439.
%e 11 is in the sequence since uphi(11) * usigma(11) = 10 * 12 = uphi(12) * usigma(12) = 6 * 20 = 120.
%t usigma[n_] := If[n == 1, 1, Times @@ (1 + Power @@@ FactorInteger[n])];
%t uphi[n_] := (Times @@ (Table[#[[1]]^#[[2]]  1, {1}] & /@ FactorInteger[n]))[[1]]; u[n_] := uphi[n]*usigma[n]; aQ[n_] := u[n] == u[n + 1]; Select[Range[10^6], aQ]
%Y Cf. A034448, A047994, A244439.
%K nonn
%O 1,1
%A _Amiram Eldar_, Dec 29 2017
