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%I #6 Dec 12 2017 00:28:44
%S 0,1,2,3,3,5,4,5,6,7,4,9,6,7,9,9,5,11,6,11,12,9,4,13,11,10,10,13,6,17,
%T 8,11,12,10,11,19,9,9,12,17,8,19,8,13,19,11,4,19,14,18,13,16,6,17,15,
%U 19,16,11,4,25,12,11,20,17,16,23,8,14,12,21,8,25,12,12,21,17,14,22,8,23,20
%N a(n) = Sum_{d|n} tau(d-1).
%H G. C. Greubel, <a href="/A086898/b086898.txt">Table of n, a(n) for n = 1..10000</a>
%t a[n_] := DivisorSum[n, If[# == 1, 0, DivisorSigma[0, # - 1]] &]; Array[a, 100] (* _G. C. Greubel_, Dec 11 2017 *)
%Y Cf. A000005, A049822.
%K nonn
%O 1,3
%A _Vladeta Jovovic_, Aug 23 2003
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