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%I #17 Mar 22 2020 12:18:23
%S -2,0,0,20,0,82,0,124,60,174,0,550,0,298,286,588,0,1030,0,1178,482,
%T 642,0,2702,260,862,726,2030,0,3824,0,2540,1018,1398,934,6298,0,1714,
%U 1358,5810,0,6632,0,4406,3628,2442,0,11870,700,5294,2182,5930,0,10192,1902,10038,2666,3774,0,22644,0,4282,6140,10540,2506
%N a(n) = A000203(n)^2 - A001157(n) - 2n = sigma(n)^2 - sigma_2(n) - 2n.
%C For primes p, a(p) = 0, otherwise positive, except for n = 1 where it is negative.
%H Amiram Eldar, <a href="/A066294/b066294.txt">Table of n, a(n) for n = 1..10000</a>
%t a[n_] := DivisorSigma[1,n]^2 - DivisorSigma[2,n] - 2n; Array[a, 65] (* _Amiram Eldar_, Jul 31 2019 *)
%o (PARI) a(n) = sigma(n)^2 - sigma(n, 2) - 2*n; \\ _Michel Marcus_, Mar 22 2020
%Y Cf. A000203, A001157.
%K sign
%O 1,1
%A _Labos Elemer_, Dec 12 2001
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