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A116009 Numbers k such that k + sigma(k) + phi(k) is a square. 3
3, 81, 400, 972, 1209, 1276, 1480, 1833, 2700, 3408, 4080, 4345, 6321, 6498, 6885, 8673, 8697, 10257, 12325, 13192, 13240, 13409, 14496, 14560, 16932, 17232, 18168, 18904, 19140, 19344, 20196, 22896, 23568, 23920, 27001, 27313, 28305 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

EXAMPLE

81 + sigma(81) + phi(81) = 16^2.

MATHEMATICA

Select[Range[30000], IntegerQ@Sqrt[# +DivisorSigma[1, #]+EulerPhi[#]] &] (* Amiram Eldar, Aug 13 2019 *)

PROG

(PARI) isok(n) = issquare (n + sigma(n) + eulerphi(n)); \\ Michel Marcus, Jan 26 2014

CROSSREFS

Cf. A116007, A116008.

Sequence in context: A274567 A137994 A074386 * A068562 A123656 A229842

Adjacent sequences:  A116006 A116007 A116008 * A116010 A116011 A116012

KEYWORD

nonn

AUTHOR

Giovanni Resta, Feb 13 2006

STATUS

approved

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Last modified September 29 16:23 EDT 2022. Contains 357090 sequences. (Running on oeis4.)