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A043293 Numbers n such that lcm(sigma(n),phi(n)) is a perfect square. 1
1, 3, 10, 17, 70, 170, 210, 357, 364, 416, 456, 577, 679, 1092, 1154, 1358, 1672, 1705, 1820, 2280, 2387, 2565, 2652, 2835, 2885, 2910, 3395, 3570, 4212, 4577, 4774, 4947, 5016, 5044, 5115, 5130, 5412, 5670, 5770, 5863, 6188, 6790, 7072, 7161, 7471, 7546 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

If n is in the sequence and n>10 LCM(sigma(n),phi(n))==0 (mod 6)

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

FORMULA

n such that sqrt(A009286(n))=floor(sqrt(A009286(n)))

MATHEMATICA

Select[Range[8000], IntegerQ @ Sqrt @ LCM[EulerPhi[#], DivisorSigma[1, #]] &] (* Amiram Eldar, Aug 12 2019 *)

CROSSREFS

Cf. A009286.

Sequence in context: A334964 A309351 A003615 * A208894 A178644 A128701

Adjacent sequences:  A043290 A043291 A043292 * A043294 A043295 A043296

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Apr 04 2002

STATUS

approved

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Last modified October 20 00:37 EDT 2021. Contains 348098 sequences. (Running on oeis4.)