A007517 - OEIS

A007517

a(n) = phi(n) * (sigma(n) - n).

0, 1, 2, 6, 4, 12, 6, 28, 24, 32, 10, 64, 12, 60, 72, 120, 16, 126, 18, 176, 132, 140, 22, 288, 120, 192, 234, 336, 28, 336, 30, 496, 300, 320, 312, 660, 36, 396, 408, 800, 40, 648, 42, 800, 792, 572, 46, 1216, 336, 860, 672, 1104, 52, 1188, 680

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OFFSET

1,3

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A000010(n)*A001065(n). - Michel Marcus, Mar 22 2018

Sum_{k=1..n} a(k) ~ c * n^2 / 3, where c = A065465 - A059956 = 0.273586... . - Amiram Eldar, Dec 04 2023

MAPLE

with(numtheory): seq(phi(n)*(sigma(n)-n), n=1..60); # Muniru A Asiru, Mar 22 2018

MATHEMATICA

Table[EulerPhi[n](DivisorSigma[1, n]-n), {n, 60}] (* Harvey P. Dale, Mar 16 2013 *)

PROG

(GAP) List([1..60], n->Phi(n)*(Sigma(n)-n)); # Muniru A Asiru, Mar 22 2018

(PARI) for(n=1, 50, print1(eulerphi(n)*(sigma(n) - n), ", ")) \\ G. C. Greubel, Mar 22 2018

CROSSREFS

Cf. A000010, A000203, A001065, A059956, A065465.

Sequence in context: A222423 A059909 A145177 * A072946 A134000 A127730

Adjacent sequences: A007514 A007515 A007516 * A007518 A007519 A007520

KEYWORD

nonn,easy

AUTHOR

Walter Nissen

STATUS

approved