%I #10 Sep 08 2022 08:45:08

%S 0,0,1,2,3,2,5,8,9,6,9,12,11,10,17,24,15,18,17,28,27,18,21,40,35,22,

%T 45,44,27,34,29,64,47,30,61,72,35,34,57,88,39,54,41,76,99,42,45,112,

%U 77,70,77,92,51,90,105,136,87,54,57,132,59,58,153,160,127,94,65,124,107,122,69

%N a(n) = phi(n)*d(n) - n.

%C It is known that a(n) >= 0.

%D D. S. Mitrinovic et al., Handbook of Number Theory, Kluwer, p. 10.

%H G. C. Greubel, <a href="/A079535/b079535.txt">Table of n, a(n) for n = 1..10000</a>

%t Table[EulerPhi[n]*DivisorSigma[0, n] - n, {n, 1, 80}] (* _G. C. Greubel_, Jan 14 2019 *)

%o (PARI) vector(80, n, eulerphi(n)*sigma(n,0) - n) \\ _G. C. Greubel_, Jan 14 2019

%o (Magma) [EulerPhi(n)*DivisorSigma(0,n) - n: n in [1..80]]; // _G. C. Greubel_, Jan 14 2019

%o (Sage) [euler_phi(n)*sigma(n, 0) - n for n in (1..80)] # _G. C. Greubel_, Jan 14 2019

%Y Cf. A000010, A000005, A062355.

%K nonn

%O 1,4

%A _N. J. A. Sloane_, Jan 23 2003