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%I #19 Apr 21 2020 19:50:58
%S 0,3,8,21,24,60,48,105,104,162,120,308,168,312,336,465,288,663,360,
%T 798,640,756,528,1380,744,1050,1040,1512,840,2088,960,1953,1536,1782,
%U 1632,3185,1368,2220,2128,3510,1680,3936,1848,3612,3432,3240,2208,5828,2736,4557
%N a(n) = (n-1)*sigma(n) where sigma is the sum of divisors A000203.
%H D. B. Lahiri, <a href="https://doi.org/10.1017/S0004972700042179">Some arithmetical identities for Ramanujan's and divisor functions</a>, Bulletin of the Australian Mathematical Society, Volume 1, Issue 3 December 1969, pp. 307-314. See Theorem 1 p. 308.
%F G.f.: Sum_{k>=2} (k^2 - 1) * x^k / (1 - x^k)^2. - _Ilya Gutkovskiy_, Apr 15 2020
%F a(n) = A064987(n) - A000203(n). - _Omar E. Pol_, Apr 15 2020
%t a[n_] := (n - 1) * DivisorSigma[1, n]; Array[a, 50] (* _Amiram Eldar_, Apr 15 2020 *)
%o (PARI) a(n) = (n-1)*sigma(n);
%Y Cf. A000203 (sigma), A064987 (n*sigma(n)).
%Y Partial sums give A332264.
%K nonn
%O 1,2
%A _Michel Marcus_, Apr 15 2020
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