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%I #8 Mar 17 2017 21:58:26
%S 0,4,18,52,100,202,294,500,666,1004,1210,1834,2028,2846,3268,4340,
%T 4624,6358,6498,8652,9132,11378,11638,15530,15100,18932,19620,24062,
%U 23548,30452,28830,36084,36076,42776,42044,53350,49284,59930,59844,71500,67240,84188
%N a(n) = sigma_3(n) - sigma_2(n).
%F G.f.: Sum_{k>=1} k^2*(k - 1)*x^k/(1 - x^k). - _Ilya Gutkovskiy_, Mar 17 2017
%Y Cf. A001157, A001158.
%K nonn
%O 1,2
%A _N. J. A. Sloane_, Mar 20 2004