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%I #18 Jun 29 2023 13:22:03
%S 0,0,1,0,0,2,0,1,3,0,0,4,1,0,5,2,0,7,0,0,7,0,1,11,0,2,9,1,0,10,0,4,12,
%T 0,0,14,0,1,16,5,0,14,1,0,15,2,0,23,0,0,17,4,1,21,0,9,19,1,0,20,0,0,
%U 22,8,5,24,0,1,26,0,0,37,1,0,25,2,0,33,0,10,27,0,1,31,0,2,29,12,0
%N Expansion of Sum_{k>0} k * x^(3*k) / (1 - x^(5*k)).
%H Seiichi Manyama, <a href="/A363899/b363899.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = Sum_{d|n, n/d==3 mod 5} d.
%F G.f.: Sum_{k>0} x^(5*k-2) / (1 - x^(5*k-2))^2.
%t a[n_] := DivisorSum[n, # &, Mod[n/#, 5] == 3 &]; Array[a, 100] (* _Amiram Eldar_, Jun 27 2023 *)
%o (PARI) a(n) = sumdiv(n, d, (n/d%5==3)*d);
%Y Cf. A363897, A363898, A363900.
%Y Cf. A001878, A284281.
%K nonn
%O 1,6
%A _Seiichi Manyama_, Jun 27 2023