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 A152218 Numbers n such that sigma_2(n)*sigma_1(n)/sigma_0(n) is a perfect square. 1
 1, 4, 529, 2116, 2583, 3249, 3346, 6150, 10332, 12474, 12792, 12996, 28224, 38240, 59245, 85905, 91035, 103607, 142560, 176382, 212949, 236980, 249744, 343620, 360096, 364140, 379050, 414428, 450840, 751530, 787710, 788424, 851796, 1059474, 1132096, 1366407 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Donovan Johnson, Table of n, a(n) for n = 1..200 FORMULA {n: A001157(n)*A000203(n)/A000005(n) in A000290}. MATHEMATICA fQ[n_] := IntegerQ[ Sqrt[ DivisorSigma[2, n] DivisorSigma[1, n]/DivisorSigma[0, n]]]; k = 1; lst = {}; While[k < 1132096, If[ fQ@k, AppendTo[lst, k]; Print@k]; k++ ]; lst (* Robert G. Wilson v, Sep 10 2010 *) Select[Range[137*10^4], IntegerQ[Sqrt[(DivisorSigma[2, #]DivisorSigma[ 1, #])/ DivisorSigma[ 0, #]]]&] (* Harvey P. Dale, Jun 18 2018 *) CROSSREFS Cf. A000005, A001157, A000203, A140480. Sequence in context: A257922 A083284 A350613 * A152463 A295206 A209608 Adjacent sequences:  A152215 A152216 A152217 * A152219 A152220 A152221 KEYWORD nonn AUTHOR Ctibor O. Zizka, Nov 29 2008 EXTENSIONS Correct definition recovered by Jack Brennen 12 more terms from R. J. Mathar, Aug 25 2010 More terms from Robert G. Wilson v, Sep 10 2010 STATUS approved

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Last modified August 17 12:30 EDT 2022. Contains 356189 sequences. (Running on oeis4.)