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

1,2

Links

Table of n, a(n) for n=1..50.

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.

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

Mathematica

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

Prog

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

Crossrefs

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

Partial sums give A332264.

Sequence in context: A075719 A245205 A101643 * A046815 A203848 A160404

Adjacent sequences: A334133 A334134 A334135 * A334137 A334138 A334139

Keyword

nonn

Author

Michel Marcus, Apr 15 2020

Status

approved