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%I #8 Aug 18 2021 09:29:31
%S 3,24,72,177,285,621,813,1278,1785,2541,2973,4653,5241,6585,8313,
%T 10266,11238,14787,15987,19767,22839,25863,27591,35031,37914,42030,
%U 46830,53550,56250,68346,71418,79419,86331,93135,100047,117792,122124,130524,139932,156672
%N a(n) = Sum_{k=1..n} sigma(k)*sigma(2*k), where sigma(n) = A000203(n) is the sum of the divisors of n.
%F a(n) ~ 2*zeta(3)*n^3.
%t Accumulate[Table[DivisorSigma[1,k] * DivisorSigma[1,2*k], {k, 1, 100}]]
%o (PARI) a(n) = sum(k=1, n, sigma(k)*sigma(2*k)); \\ _Michel Marcus_, Aug 18 2021
%Y Cf. A000203, A024916, A065764, A072379, A074285, A326123, A326124, A330322, A346865.
%K nonn
%O 1,1
%A _Vaclav Kotesovec_, Aug 18 2021