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A110601 a(n) = phi(n)*tau(n)^2, where phi is Euler's totient function and tau(n) is the number of divisors of n. 2
1, 4, 8, 18, 16, 32, 24, 64, 54, 64, 40, 144, 48, 96, 128, 200, 64, 216, 72, 288, 192, 160, 88, 512, 180, 192, 288, 432, 112, 512, 120, 576, 320, 256, 384, 972, 144, 288, 384, 1024, 160, 768, 168, 720, 864, 352, 184, 1600, 378, 720, 512, 864, 208, 1152, 640 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..2000

S. Porubsky and M. G. Greening, Problem E2351, Amer. Math. Monthly, 80, 1973, p. 436.

EXAMPLE

a(4)=18 because phi(4)=2 and tau(4)=3.

MAPLE

with(numtheory): a:=n->phi(n)*tau(n)^2: seq(a(n), n=1..70);

MATHEMATICA

Table[EulerPhi[n]DivisorSigma[0, n]^2, {n, 60}] (* Harvey P. Dale, Nov 29 2011 *)

PROG

(PARI) a(n) = eulerphi(n)*numdiv(n)^2; \\ Michel Marcus, Jun 21 2017

(MAGMA) [EulerPhi(n)*NumberOfDivisors(n)^2: n in [1..60]]; // Vincenzo Librandi, Jun 21 2017

CROSSREFS

Cf. A062355, A035116.

Sequence in context: A312824 A312825 A312826 * A107926 A174741 A312827

Adjacent sequences:  A110598 A110599 A110600 * A110602 A110603 A110604

KEYWORD

nonn,mult

AUTHOR

Emeric Deutsch, Jul 29 2005

STATUS

approved

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Last modified June 18 07:25 EDT 2021. Contains 345098 sequences. (Running on oeis4.)