A043293 Numbers n such that lcm(sigma(n),phi(n)) is a perfect square.

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

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