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A062784 Numbers k such that sigma(k) + phi(k) is a perfect square. 2
2, 4, 56, 110, 125, 161, 287, 391, 418, 423, 511, 588, 609, 675, 721, 799, 910, 935, 1048, 1057, 1102, 1130, 1281, 1351, 1457, 1485, 1630, 1716, 1799, 1826, 1921, 2047, 2060, 2177, 2255, 2378, 2403, 2449, 2457, 2472, 3199, 3266, 3915, 4010, 4376, 4417 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Harry J. Smith, Table of n, a(n) for n = 1..1000

MATHEMATICA

Select[Range[4500], IntegerQ[Sqrt[DivisorSigma[1, #]+EulerPhi[#]]]&] (* Harvey P. Dale, Jan 18 2012 *)

PROG

(PARI) select(k->issquare(sigma(k) + eulerphi(k)), [1..5000])

CROSSREFS

Cf. A065387.

Sequence in context: A121234 A084574 A087621 * A318642 A230884 A185182

Adjacent sequences:  A062781 A062782 A062783 * A062785 A062786 A062787

KEYWORD

nonn

AUTHOR

Jason Earls, Jul 18 2001

STATUS

approved

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Last modified June 23 05:11 EDT 2021. Contains 345395 sequences. (Running on oeis4.)