A334136 a(n) = (n-1)*sigma(n) where sigma is the sum of divisors A000203.

0, 3, 8, 21, 24, 60, 48, 105, 104, 162, 120, 308, 168, 312, 336, 465, 288, 663, 360, 798, 640, 756, 528, 1380, 744, 1050, 1040, 1512, 840, 2088, 960, 1953, 1536, 1782, 1632, 3185, 1368, 2220, 2128, 3510, 1680, 3936, 1848, 3612, 3432, 3240, 2208, 5828, 2736, 4557

Offset: 1

Author

Michel Marcus, Apr 15 2020

Keywords

• nonn

Links

• D. B. Lahiri, Some arithmetical identities for Ramanujan's and divisor functions, Bulletin of the Australian Mathematical Society, Volume 1, Issue 3 December 1969, pp. 307-314. See Theorem 1 p. 308.

Crossrefs

Cf. A000203 (sigma), A064987 (n*sigma(n)).

Partial sums give A332264.

Programs

Mathematica

a[n_] := (n - 1) * DivisorSigma[1, n]; Array[a, 50] (* Amiram Eldar, Apr 15 2020 *)

PARI

a(n) = (n-1)*sigma(n);

Formula

G.f.: Sum_{k>=2} (k^2 - 1) * x^k / (1 - x^k)^2. - Ilya Gutkovskiy, Apr 15 2020

a(n) = A064987(n) - A000203(n). - Omar E. Pol, Apr 15 2020