This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A334136 #19 Apr 21 2020 19:50:58 %S A334136 0,3,8,21,24,60,48,105,104,162,120,308,168,312,336,465,288,663,360, %T A334136 798,640,756,528,1380,744,1050,1040,1512,840,2088,960,1953,1536,1782, %U A334136 1632,3185,1368,2220,2128,3510,1680,3936,1848,3612,3432,3240,2208,5828,2736,4557 %N A334136 a(n) = (n-1)*sigma(n) where sigma is the sum of divisors A000203. %H A334136 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 A334136 G.f.: Sum_{k>=2} (k^2 - 1) * x^k / (1 - x^k)^2. - _Ilya Gutkovskiy_, Apr 15 2020 %F A334136 a(n) = A064987(n) - A000203(n). - _Omar E. Pol_, Apr 15 2020 %t A334136 a[n_] := (n - 1) * DivisorSigma[1, n]; Array[a, 50] (* _Amiram Eldar_, Apr 15 2020 *) %o A334136 (PARI) a(n) = (n-1)*sigma(n); %Y A334136 Cf. A000203 (sigma), A064987 (n*sigma(n)). %Y A334136 Partial sums give A332264. %K A334136 nonn %O A334136 1,2 %A A334136 _Michel Marcus_, Apr 15 2020