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A334136 a(n) = (n-1)*sigma(n) where sigma is the sum of divisors A000203. 1
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified July 30 05:36 EDT 2021. Contains 346349 sequences. (Running on oeis4.)